Things to work on:
-you have an arch in your back. This puts all the pressure on your lower back and disrupts the natural movement of the horse, preventing him from properly reaching out with his hind legs. Move your seat more under you to relieve this pressure.
-Lean back and sit deep, your seat should absorb and move with his motion.
-have more weight in your heels and lengthen down your calf, especially over the jump.
-you may need to lengthen your reins for this, but you need to keep your hands closer to you and off of him unless you are 2 point. When your hands are stuck to his neck, his mouth bumps against your hands and he can't get contact, making him have to pivot around that spot and lose balance. There should be a line between his mouth and your hand, and the reins should feel like a stretchy band as your arms softly move with his motion.
-don't perch on your hands. Keep your thumbs up, not in. Make sure not to break the line at your wrist.
-keep your toes parallel instead of facing out.
-avoid pinching with your knees.
For the horse:
-you want him to feel in front of your leg. Right now he doesn't have much impulsion.
-keep him light on the forehand, so he isn't leaning on the bit.
-work on rounding his hind under him. Also, as a general rule you should ride more with your outside rein than your inside. If he is truly in contact, you should be able to drop your inside rein without him changing his frame.
You pretty much said everything but I have one more:
- RELAX: You seem a little stiff and "pinchy" if that makes sence. Your arms are really heavy and stiff on the bit as well. You really perch on your horses mouth, like Roro said above.
To help you relax and feel your horses movement better, try riding bareback a few times. (If that is possible for you and your horse to do safely.) When you do that, make sure you stretch your legs down and relax :) I do this all the time and it really helps me out.
Also, to help your arms and even your back, try riding with a crop on your back and keep it up by hooking your elbows around it. It should put your arms and shoulders in the right position when you put a little pressure on it. Even if you don't ride with it, try it in front of a mirror and get a feel for how your arms and shoulders feel. (For a bonus, it's a really good back stretch (: )
Overall, though, you seem to be a good rider. Keep up the good work on your very cute horse :)