definitely jump without stirrups, and if you're able try doing that through grids
Walk trot and canter at the two point and make sure your back isn't rounded and push your hips back
Definitely ab workouts! A strong core makes a huge difference! As well as lots of no stirrup work to help keep that leg still!
When i was learning my trainer used to have me do walk, trot and canter laps in 2 point this help me so much to balance 😊