It's incredible how much things can change in a day.
Dad went home today, and for the first time, he said that he understands that he had an accident and that he needs therapy. He knows that he can't go back to work for a while and needs to rest, and he understands that even though he doesn't remember the accident, everyone is telling him the truth. He's happy to be home, and is not arguing or getting upset at the mention of his short term memory loss. He's still a bit muddled, and says weird random things that don't make sense, but it sounds like he's progressing more and more each day. Just the fact that he's not refusing outpatient therapy, and that he understands he's not allowed to drive, make me feel loads better.
I talked to my Mom, and she sounded the most optimistic I've ever heard her. It really made me feel better. Dad is letting her cook dinner for him before she goes home tonight, so there's no danger of him forgetting to turn off the stove or something. The battery has been removed from his car, just in case he does try to drive.
Anyway, I hope this is an indication that things are going to continue to gradually improve. I'm taking his acceptance of his situation as a good sign. If things continue to improve, and he's able to take care of himself, I won't have to move home after all.