Ok first I want to point out in your post that you said when you stand up hell take off....his take off is what should close your hip angle for you, there should be no you stand and then he takes off, It happens together but because of HIS action. If you act first your jumping ahead.
Ok, for greenies I don't worry about takeoff spots. They need to figure out on their own their natural ability to jump, if you take a green horse and fight and fight them up to the fence for that perfect spot that you see your going to make them sour. Since he's so new let him figure it out, hell find whats comfortable for him. Im not saying be a complete passenger though either. Ride him at a medium trot up to it, try not to let him get slower or quicker. Since your worried about hitting him still go into two point ahead of time. Id say go in about 3 strides out and stay in it about 3 strides after as well. Once he's used to a certain jump go ahead and ride normal to it and go into two point when he takes off. If you introduce a new fence, its just safer to go back to two point beforehand if you are afraid hell over jump it or wiggle around etc. Just make sure your still riding effectively in two point! Your being safe and nothing wrong with that. Now don't do it for 5 months or anything lol, but since he's just starting out its a perfect way to let him figure it out without interfering or punishing! That's how I jump all my greenies to start with. I set up a small jump with poles before and after to help with striding. Its best to have someone on the ground to watch though to be sure the distance is correct because not every horse is the same in stride length.
Simply Sophisticated-"Sophie" 2003 FSH mare.
Seize the Moment-"Leo" 2010 KSH gelding