Well, let's see, if you've already tried dishwashing liquid, dishwasher detergent, baking soda, vinegar, ammonia, napalm, etc. There's another thing I would suggest. I am an avid yard sale shopper and frequently come across casserole dishes and other glass cookware that is extremely dirty and/or has a thick layer of cooked-on gunk.
What I do to clean these icky things is to spray them quite heavily with Easy-Off oven cleaner, seal them in a plastic trash bag (a small one) and seal the bag. I let the piece stay in the sealed bag at least 24 hours. After that period of time, I take it out and wash/scrub it in hot soapy water. If there's still stuff on the piece, it gets another treatment. I have had it take several iterations before I'm left with a "like new" casserole or whatever.
Seems to me that if you've messed up the casserole, you really have nothing to lose by trying just about anything. If nothing works, then you're stuck with buying another dish. I'd say go for it and try anything that's suggested.
Katie
P.S. I've used this same method on stainless steel cookware, too. Just don't get it on any plastic, Bakelite, etc. knobs and handles.