Way to go in holding the boundary with your mother; that had to have felt really good indeed. She must have been disconcerted to find herself dead in the water!
And I am sorry about the way it went with your dad .... he does sound quite limited/handicapped when it comes to understanding relationships and communication, very tactless and oblivious, but probably not deliberately malicious, if I get the right perception here. But it was nice I guess that he was able to realize afterwards that he must have been hurtful, to seemingly regret it, and to understand an apology would be a good course of action. Maybe approaching death makes him feel more regret about it and want to try to not totally lose/destroy whatever relationships he has before his time comes .....
I see how you'd feel torn. I guess the thing to do (at least I guess how I'd try to approach it) is to be as gracious as possible in accepting his apology at face value, be as compassionate as possible, not withhold visits but probably limit the amount of time you spend, just for your emotional health/sanity.