Hi & welcome,
Agree with others for the most part but a few thoughts to add/consider. First & foremost, I STRONGLY suggest you find a good trainer/instructor to help you learn, because all the best written tips in the world pale compared to hands on, first hand help.
Mounting: He REFUSES to stand still. Won't do it, never has. Takes me 5-10 minutes to get on, and when I do, he backs up, goes forward, turns around, and is generally agitated by my presence.
This may be just one more eg of him trying to assert himself. But consider other possible reasons. ESP as you say he's never been good at this. Not standing to be mounted & being generally 'antsy' under saddle is very frequently to do with pain. So rule that out/treat it first. ESP if he's an ex racer, there are likely body issues that may not have been addressed.
I suggest using a mounting block(log, fence, whatever) as a rule, to reduce possible mounting discomfort. Just because you CAN get on from the ground doesn't mean you should, or it will be comfortable for him - even assuming perfect saddle fit & no back/body issues, especially if you always mount from the same side. Especially if you are a big person. If say, you were a 5' featherweight, then that probably wouldn't be such a consideration.
He may also have never been taught to stand for mounting, or that he can relax and stand under a rider.
At first, perfect trail riding, calm, collected. Now, he randomly bucks, lifts a leg, crabs, and kicks out at the other horses (whom he lives with) on trail.
That all sounds like it could be due to pain, esp if his behaviour has changed with horses he knows well.
It can get quite scary, especially whilst along cliffs and rivers on a narrow path...I've checked his tack (all new), fitting, burrs, etc, but can't see why he's so bent out of shape. He also tries to bite my legs when we stop, only he can't reach
He nips sometimes, but passively.
I find it difficult to understand how you can call that 'passive'. You also mentioned slobber on your sleeve. I would sit down & have a hard think about the 'manners' you want and how you're going to enforce - and reward - them consistently. For safety's sake, regardless of whether you mind slobber & him getting in your space, keeping his mouth away from you at all times & keeping him at arms length unless you get in his space or you expressly ask him to be closer are among the manners I think very important.
Re punishment for Wrong behaviours, timing is SO important and punishing after the event is not so effective, even if it's only by a second or few. Horses need instant associations & it's best to set it up that the horse punishes *himself* as he *starts* the behaviour if possible. Eg if he nips you & you're holding a wire brush or such - ouch! He's less likely to try that again!
overall, I still think he's a great horse. Even on his worst day, he's still more-or-less manageable and never outright mean or vicious.
For fear of sounding... Fluffy
I'm sure he's a great horse! Just that horses learn to do what's good for them & quit doing what isn't. So even if he were 'outright mean' you've got to ask yourself whats been going on that he's *learned* the necessity & effectiveness of that behaviour??
What worries me is just that things are getting progressively WORSE all the time...I'd appreicate any thoughts on how to improve this!
You haven't told, aside from saying you smack him for biting etc, what you've so far done/tried to fix it? Posted via Mobile Device