I'd plan on starting over. With that shallow of water, it'd be a great time to drain and make it deeper. I'd cut my losses, forget about the aeration system that you've got going and do some planning.
At 6'-8' deep, I think you really aren't deep enough for your winters. While an aeration system might prevent most winterkill, if it's a long, cold winter, that shallow of a pond will get pretty chilly for the fish.
