Originally Posted by paulri
Well I took it to a transmission shop, and they said there is no crack, it was just "casting," ...
Glad it's just that. Was going to tell you if you run your finger over it and it felt raised, likely casting. Recessed something else, but even then I didn't consider it necessarily dire. Agree with the hallstevenson, while the shop had it up should have had them loosen the plug.
I think with the options listed, using one them you should be able break it loose and get to the d&f. I watched a youtube think it was your year Civic, guy used a rubber mallet to the ratchet on that one.