Okay, well, you said it yourself: your jumping position needs alot of work. I would stick to groundpoles and work on your position - your stirrups could go two holes higher, you have too much foot in your stirrups, your back should be arched, and your shoulder should be more open. You're not releasing with your hands, your leg is swinging back, and you're sitting back in the saddle too quickly. I would definitely not do combinations yet.
However, your flatwork looks solid! I'm assuming this video was made when you were super new to jumping. Everyone makes loads of mistakes when learning how to jump! I would love to see a more recent video to see the improvement!