I agree with all of the above.
One quick comment on your position. You are grabbing too much with your knees. Thai has loosened your lower leg allowing it to slide back over the jump. You are "pivoting" on your knee. This destabilizes your position a LOT causing your upper body to topple forward. Then, you have to rely on your crest release to hold up your upper body.
Grabbing with knee, toppling forward, leg sliding back
This photo isn't perfect, by a long shot. I am no equitation rider. But, the knee is more relaxed and flexible, my lower leg is closer to the girth, my seat is further back over the saddle, and I am not relying on my crest release to support my upper body weight. I am in a more balanced position.
You need to relax the grip of your knees and allow them to be more flexible...allowing your seat to move back more over the saddle. Then, you need to concentrate on keeping your lower leg at the girth! Then, you will be able to wrap your leg around the horse, settle into the stirrups with your weight and develop a bombproof position.
Riding without your reins, with your arms out like an airplane, (in both two point and over jumps) will help you develop a more solid lower leg.
Your horse has the beginnings of some decent form, when she gets to the jump with the correct distance and better impulsion.
I am not a western breed jumper rider, so don't have the proper appreciation of the long and low and slow approach to jumping, so cannot offer much critique in that department.
But, you two look like a really nice pair with some future.