Use or don't use vacuum advance on distributor???????????????????

Your car should run good without the vacuum advance hooked up. I can go to any great running motor, unhook the VA and it will still run great. I think your battling more than one problem.
Forget the VA for now. Get the initial timing set, and the total timing set. Then, I'd look into fuel delivery. Maybe a buddy will loan you a carb that has been proven to be a good carb, and start there.
P.S. - a 750 dp carb will run just fine on your stock 360 magnum. Maybe not that particular carb, but in general, a 750 dp holley will work just fine.