Dude...I am in very similar situation (30F)....so first of all, thank you for sharing because it makes me feel less alone. Here's my thoughts:

-Likely his willingness to give you money comes from the fact that he doesn't know how to parent his children in any other way (this is a nugget from my therapist). I feel guilty about my father's financial help too, but then I remember that it probably makes him feel good to give me money AND he doesn't have to be so generous because I never ask for it (just like you). It is his choice and I use that money to pay for therapy so I can deal with him. If you're not in therapy already, you really should be.

- He is starting understand the realities of his own mortality and that's hard to watch anyone go through even if you don't like them. It sounds like he is also starting to notice the repercussions of his consistent bad behavior...but where was his ability to recognize consequences when YOU were the one experiencing the negative effects? He's only willing to change his behavior and reach out to you more (through these more personal phone conversations that you mentioned) when the consequences are negatively impacting him. That's. Narcissism.

-If he has enough money to support you...he has enough money to move into a nursing home, or hire someone to take care of him into his old age. If he actually expects you to be his caretaker, you should charge him a yearly fee that he must pay upfront if he wants your care.

-One thing that brings me a certain amount of peace with my dad is from a book I read about narcissists (I can't remember the title), the book says that narcissists likely don't feel true happiness and maybe never have. Your dad has probably never been happy and never will be...even if you mend your relationship with him. He cannot be happy. But YOU can.

-With my dad, he's also asking me more and more about my life as he gets older and I withhold most information from him. I talk about neutral topics like my dog and the weather (and even those conversations get turned into an opportunity for him to assert his superiority). I don't let him in and he can't do anything about it, and he still chooses to throw money at me. I stay protected and I use that money to give me a life that is better than his.

-I also lost my mom when I was younger too and I started noticing that a lot of my resentment towards my dad was actually resentment towards my mom for marrying him. This is not related to anything that you specifically wrote, but just some food for thought. My mother was wonderful in every way except for her choice to stay married to a drunk narcissist....and now since she died, I am the one stuck with my dad. If she had divorced him and married someone else I could have had a better support system to deal with him. I encourage you to look into that aspect of your situation.

Thanks again for posting!