Based on how you described the carb to begin with and now with a stuck piston, I'd chunk it and start with another one. Heck, anything you started with would probably be better than yours.
There's probably some pitting in the body too, so you're going to have problems with it even if you get the piston out. Like Kurt51 says, they're giving away old "B" models. Get yourself another good one and start fresh.
Just my opinion and worth every penny you paid for it.
