I agree about the stirrups, definitely drop them a hole!
As for your ankles, I can understand with past injuries the difficulty you have. I find standing on the bottom step of a staircase and stretch your heels down (best to hold onto something!!) until you feel the tension, then holding it for a bit, is a really good exercise to get more flexibility and strength in your ankles.
Once you have your strength back, I would like to see you drop your weight into your stirrups, stretching your heel down and wrapping your calves around your horse's barrel. That should help you with keeping your *booty* over the seat of the saddle, and avoid jumping ahead.
I also noticed your shoulders rounded in most of the photos, so really work on stretching your shoulder blades down and opening your chest up.
Your release is effective and I really like that you have enough core strength to hold a steady upper body!
Overall very nice! A few things to work on but they are mostly strength related so it's up to you to get working out!
Good luck :)