as far as my arm swing i think the bottom of it is muscled/controlled but i try hard to keep the beginning free. it seems hard to have a completely free swing unless im throwing the ball straight at spares or throwing end over end strike ball that i practice from time to time. it seems like the stronger the finger position i try to keep the more muscled my swing becomes (even though i still get more revs)
The reason your swing gets more muscled when you try to put more revs on it is because you are trying to put revs on it instead of just keeping your wrist in position and letting the ball just roll off your hand. It takes much practice and patients to learn to do this and everybody seems to have this problem from time to time. You have to learn to build trust that if you keep your wrist and hand in position to the release point that the ball will hook, it may take a long while to build up this trust, but when you do your scores will take off, so stay with it at least in practice.
Your balance arm needs to be up and out at shoulder height, keeping your balance arm down causes your weight to shift too far to the right and shifts your center of gravity to the right which causes you to slide to the left. This takes much practice to get used to as well, and will help prevent soreness in your legs and back like JstevensMD said. I don't know if your back was hurting or not, but watching you bowl was making mine hurt, so please head his and my advice before you hurt yourself.