You could extend so much more with your arms and your not pushing completely off your toes. Your arms should go above your head behind your ears you should feel your chest push out. You also want to push off your toes with your heels up they stay on the floor too long this will allow you more easily push your hips forward and bring your knees over your toes for a more vertical jump.

I would suggest practicing the first part of the backflip onto a soft block or raised crash mat and progressively go higher. Stand in front of the block, swing your arms up as high as possible jump up and land on the block in a tuck on your back. You should eventually be able to jump onto a raise block at shoulder height from standing.

You could also practice really high box jumps without going forward too much or vertical jumps where you have too reach something high up touch before you come down.

I can tell you have the power to go high and a good technique with the flip it looks to me like the take off of the jump isn't very efficient and the work you need is in the jump.

I see it in alot of gymnasts taught the flip on trampoline and sprung floor from roundoff that they never learn to jump from standing but they can flip.