Ok, let's figure out some of these issues...

So you might've heard about him before, but now that the weather is nice and we have a proper arena, I want to get cracking with my "greenie", quotations because it doesn't feel right calling him green.

We've had a trainer out who looked at him and said he's 'very VERY well broke' but he's got lots of little problems that need to be addressed, that I will admit probably stemmed from my mistraining.
We bought him because he was 'perfect', although he was a few hours away so we basically paid for him sight unseen, with a three month no-questions money-back guarantee, so it sounded pretty legitimate.

We got him in October of last year, he was five years old, good and sturdy with his walk/trot/canter, he'd initially been broke Western, was switching to English and they'd had him jumping to 3'6 with "potential to go higher", he was five at the time, and still labelled green broke.
We didn't do too much though the winter- we didn't have a proper arena, but we rode when we could, and in the beginning of summer things were rusty but not terrible, so we decided to just tough it out. WELL THEN, things started going hugely downhill.

PROBLEMS:
Ground manners -solved. He was pushy and disrespectful, big and he KNEW IT. He wouldn't let you put the halter on/bridle on, but I cracked down on that, and now he's A LOT better, to the point where he'll follow at a respectful distance around the field, without so much as a hand on him and stand quietly, etc.

His BIGGEST problem is that he REFUSES to move forward, and I personally think he's just being stubborn. I know he had teeth problems, they were sharp and hurting his mouth, but we got his teeth done and a week later I hoped on and he was SO. MUCH. BETTER. Before he would stop, stand in one place and refuse to move, that ride I got him to walk/trot/canter happily, but he actually worked *gasp* and decided that he didn't want to do that again, so it got progressively worse over a few days and we're back at square one.

I dont' longe, I should, but I was only recently taught and am not exactly confident. I've played around with him on a short line, halter and riding crop in an enclosed paddock and he did fine, he was moving freely and nicely at the walk and trot, paying attention and doing his work. After a week of that we moved to the arena with an actual line/whip and WOAH, he nearly pulled me over, galloped around me and started to buck/rear. I KNOW I should have stuck with it, but I don't have much experience with it and didn't know how to deal with it without getting hurt, so I handwalked him and let him go, and haven't yet gone back to the paddock.

SO, I don't think he's sore, because I KNOW he can move freely, and I know it isn't his saddle because more often than not I'm riding bareback (he's one of THOSE horses that's more like a sofa with legs).

Any suggestions on how to get him moving forward? ANYTHING AT ALL? He's built kinda downhill, but I don't think that'd be such a hue problem, haha.
HUGS IF YOU READ THIS WHOLE THING!

In reading your post, my overall impression is that this horse has your number, and that pretty much everything else your experiencing stems from that.

There are a couple of ways to deal with the underlying problem, but none of them are quick fixes.

This is a combination of 1.)respect - the horse doesn't view you as the alpha or leader and 2.) basic aids - when you ask for forward with a little aid and don't get it, do you follow up? How? Are you successful?

Rather than getting down into a detailed analysis of this and the longing problem, what I would suggest to you is that you take some lessons on a different horse not so willing to challenge your authority. Learn how to *insist* on forward, and learn how to establish your authority over the horse. Then come back to this horse and apply your new skills. Make sure your instructor understands what you're trying to gain from the lessons and matchs you with horse that will challenge you within your ability.

Right now you perceive the horse as being stubborn; but a horse that doesn't respect your aids and you can't move forward off of your leg easily moves from stubborn to unpleasant to dangerous pretty quickly. I'd say your horse is not a greenie and was well-broken by an authorotative horseperson and has learned to take advantage of your more tentative handling.

1 ) I know I've got his respect on the ground, because aside from the trainer that came out once (I also need advice on how to find RELIABLE people, gah) I'm the only one who WONT let him get away with whatever it is he's trying to get away with. 2 ) Yes, I follow up. I use the ask / tell / demand (or however people around here word it) method, squeeze, kick, REALLY kick and crop.

I know how to 'insist' on forward, I took many years of lessons at various barns and at each one got to the point where I was riding the greenies, I take lessons on my other horse to keep my aids/seat well defined, and work with a trainer who wont let me NOT take authority over the horses I ride, so that's not the issue, because I'm doing/have done that.

He's moved qu+ickly from stubborn to unpleasant, I haven't seen the switch to dangerous (he still, literally, 'catches' me if I ever get off balance, as if I'm going to fall, which makes me mad because it's hard to be angry with him then).
He was wellbroken, but the rider they had on them was not an 'authoratative horseperson', and my handling is far fom tentative- I learned quickly that that's not the way to go with him.

I'm not here saying that I'm an expert, but your post really didn't help me, considering what you've suggested are things that don't define me (though I can see how you could see that they would) or I'm already doing... so you can see where I can get frustrated with not knowing what step to take from here.

OH also, sorry for the double post, but I wanted to ask...
Would this be something you'd have a chiropractor out for? He has no lameness issues, he moves (really moves) when he's out with the others and I've seen him on the longe, and he's not stiff or unbalanced, but would there be a big enough difference with a rider on his back if he's fine without?

Can you get him to even move laterally or pivot in a turn if he is refusing to go forwards?

I had one horse that refused to move forwards. He was really lazy, so everytime I booted him forwards and he refused, I made him back up. A lot. Finally it was like the lightbulb went on and he realized that it was a pain in the butt to backup, might as well listen the first time and go forwards.

If you have eliminated any medical conditions it is behavioral. Can you have a friend lunge him while you are riding?

Yeah I can, with a fair bit of effort.
I've been backing him up, but maybe not backing him up far enough. Next time I'll definitely keep him going, and keep on him about it.

Yes I can, a friend of my mothers' actually, she's a very well-established (but now-retired) trainer, so hopefully working with her will help, but I want to gather as many tips as possible, because it's getting to the point where it's just ridiculous.

Update?

I got on him the other day and he started to act up, which earned him a few hard smacks with the crop, and he trotted along after that. Threw a few little kicks, but honestly, he's so smooth I hardly noticed.

Your horse sounds so much like my friends horse...its actually almost the exact same story. And as maura suggested, I do believe he is playing you. I don't think that is his only issue but once they get that upper hand, they are very relucatant to give it back. With izzy, my friends horse, we called it 'playing the kim game'. He would refuse to let her bridle him...she had some goofy trainer out to see him about it who taught her some hair brained technique where she would spend HOURS trying to get him to take the bit on his own. Then, one day while waiting for her to tack up on a ride, I got impatient..I grabbed the bridle, told her to leave the barn and I had the bridle on him without force in 20 seconds. As soon as I 'unlocked' that for her...he has never given her any more trouble putting the bridle on. In my experience, they give you what you expect. If you are expecting him to stop and not move forward, he will do it for you. Even if you have to fake it, try being overly optimistic for just one training session. Tell yourself 'this is going to be the day that he moves out and keeps on going!" or anything that gets you into that state of mind. The days that I slip into the 'oh great, another crappy weather day where I have to ring ride...and I just KNOW he's going to be bad because the wind is going' my horse is SURE to give me a crappy ride. Even if im just out messing around with my horse I have to sometimes force myself into that 'this is going to be the greatest day EVER!" mode. I might be crazy or diluted or whatever, but its worth a try!

Like I said above, we went out and I had him moving forward, we worked on walk/trot for half an hour, ended on a good note, etc. One thing I have to say, I need longer reins. I swear he's as long as a train, and the reins I use for my other horses just don't fit.
AND to top it all off, I managed to rip a huge hole in my riding pants mounting. It started off as a badbad day and ended well.

Ill trade ya...my horse has a very short neck and even traditional 'gaming' reins are too long...lol