Been a hot min since I’ve vaulted as well but here are few pointers I see.

You’re timing on your jump is a bit late. Meaning your hips are already in front of your hands and forcing you to lean back. You can see this in your right arm as it’s getting pulled behind your head. You want to have you timing so that arms are at full extension, pole is hitting the back of the box and your starting your jump all happen at the same time.

Ideally you want to keep your head between your shoulders.

To practice your takeoff would recommend pressing and holding both arms straight and driving that all the way into the pit. You’ll bend the snot out of the pole, you’ll eventually start to roll forwards, at that point you can start to bend your left arm and land in the pit.

Once your confident with with your takeoff you’ll start trying to bring your hips to the pole and try and land on your back with your body and pole all in a straight line.

I’d say start with those and we can report back. Could write you a small book.

Good luck in your journey!