Okay sorry about late replies, I hit college in the morn, then the barn in the afternoon, then work at night, lol. Anyway it looks like you have the beginnings of "forward and round" a little mantra I live by. Remember to drive your horse into a rounder frame, its not just giving a soft rein, but animating your posting (posting higher like your scooping the horse up from beneath you) and continuing to squeeze with your calf every stride. Remember "leg to seat," legs drive, seat sets the pace. Your trotting videos however were displaying great forward motion, and I could tell your pony was considering rounding into the bit. (thats usually demonstrated by a horse that put its head down then pops it up, and back down again. That's essentially their way of processing what your asking and figuring out if rounding into collection would be more comfortable than hollowing.) So remember to engage with your calf, kick even, to bring his hind under himself. When you "scoop" up in the posting trot, your driving with your calf to "get their hind legs in front of yours," and this is only accomplished by riding him around and ecouraging collection. He has to process and then fill the gap between leg and rein. It takes a while so don't feel discouraged. Remember collection is not developed over night! Another thing to consider is conditioning him more, collection is easier grasped and defined when a horse has developed the muscles to carry itself. You can condition through "ground driving" (my personal fave), harness work on the lounge, or simply riding him under saddle through trot to canter transitions with 5 minute walk breaks between. However should you try to condition through riding, you have to make a serious effort to continue to engage his hind end. This might mean running around the ring while you kicking with your calfs at his hind so he can "get under himself," but once he does, and you can ride it for a lap or two, praise and down transition to a walk. Remember in the canter its important to sit back "deep" in the saddle, open thighs, with calfs around the barrel of the horse. Keep sitting and driving forward with your seat, and make sure your heels are down and your calf isnt swinging, otherwise you engaging a faster canter and not a rounder one. You only get round in the canter by sitting and driving with your seat. (swaying with the rocking motion of the horse) while being solid through your core and legs. Hands are a separate entity so remember soft reins, and no backwards motion. Remember to set pace and round, you have to "sit and drive," your booty should not leave that seat, and I did see it bounce a few times. Also you were on the wrong diagonal in the second vid.
Hopefully that made since, as its hard to explain collection when you have a horse under you, you can imagine how hard it is online. :/