You are doing a lot of things right, keeping your eyes/head up, your leg position doesn't look bad. Try to keep your upper body back, looks like you are anticipating his jump and leaning forward too much which inhibits his front end and causes you to have to brace on his neck. If you keep your seat closer to your saddle, and just close your hip angle, rather than letting your body go forward, you'll be more balanced and able to release without bracing. Let your elbows open up and release but keep your body more stable. He looks like he is a willing jumper. If you can, practice jumping without reins and that will help you with your balance. Happy jumping!!