You both look like a gutsy team!!
I would place your stirrup iron closer to the ball of your foot. Right now it is too far home, causing stiffness in your ankle and consequently your entire leg. You weight needs to sink into your heel and right now it can't.
Once your lower leg is corrected, you will be more able to stay with your horses motion over fences. In a few pics, her thrustiness has caused you to become left behind while in other pics, you are jumping ahead a tad. Trot lots of fences with out stirrups to strengthen your lower leg.
I would also give more of a release. You pony really cracks his back over theses fences, give him enough rein to let him reach over the fence. It looks as if you are balancing a bit on the reins to prevent your upper body from falling back, grab a bit of mane if you need to.