Buxom -- I hope your time away is giving you some time to relax some and tend to your mental health.
On the question of helping his dad, I think it's admirable you'd tell him anything other than "No way" given what's he's done to you, but then I'm just a noob making tons of mistakes every day. I think the DB way would be to look at your relationship with his father (not your relationship with your WH) and determine what you want to do or not do for the father, without regard to how it might play in the context of your marital sitch.
Me: 46 W: 44 Married: 17 Together 21 D13; S10 BD: 03.03.15 (Not attracted to you) Almost 2 years trying, alone, to save marriage Status now: Divorced (effective 06.13.17)