I have never used warm compresses on my fistula because it was never suggested. I use an ice compress only when I infiltrate and the reason is to minimize the swelling and bruising. I do light weights at the gym for general exercise and I did the squeeze ball exercises for my first fistula which was on my forearm. I now have an upper arm fistula like you and my surgeon said I didn't have to bother with the arm squeezes as upper arm fistulas tend to develop more easily without help from the ball. However I have really good flow so that might be an individual thing. The squeeze exercises won't hurt anyway and if they help to develop the fistula then that's good.
As for the aneurysms, the best way to avoid them is to make sure that the nurses don't get lazy and needle you always in the easiest place. They need to ladder the sticks slowly up the arm so the vein develops evenly instead of weakening in certain spots and bulging out.
The other option is to develop buttonholes. You use EXACTLY the same hole and same angle with the needle each time until you create more permanent channels and then a blunt needle that slips in quite easily (or is supposed to anyway). There are threads on here about buttonholes and members who use them too. Do a search and you'll find more info. I'm laddering right now to develop and strengthen my fistula but eventually will try to establish buttonholes also.
Hope this helps.