Wait, did you try the baking soda and vinegar volcano method? Because my buddy Dave once did that thinking it was some secret chef hack and it just made this weird crusty paste that baked on even harder. He was out there with a metal spatula chipping away at it like a cave man for like three hours before his wife came home and just hit it with the Dawn and some hot water. I swear he looked so defeated standing there with a chipped pan and this look like "I have a masters degree, why can't I clean a pan.
Man that's rough, four hours on something with no progress is brutal. I've been there with my own projects and it just drains you. Hopefully you got it sorted eventually or at least found a better way to tackle it.