Just saw this thread. Sorry,
@Capella to read about your situation.
My Dad was a deadbeat alcoholic. My Mom divorced him when I was 2 and raised me on her own, with no help from him. She chose not to take him to court for child support, since he really didn't have the money. When I got old enough to grasp the real situation, around age 14, I told him I didn't want to talk to him any more. He showed up at my high school graduation uninvited, but otherwise I didn't talk to him after I told him I didn't want to. Several years ago, I was contacted by a relative on his side of the family to tell me he had died. I really didn't have any emotional response. He just wasn't a person in my life and hadn't been for so long. I felt guilty for not having a reaction.
Like you, I believe I am a better person based on my experience, because I grew up wanting to ensure I wasn't like him. I have a lot of sad memories related to him, but I choose not to let them affect me. That's pretty easy at this point, given they are mostly from 40+ years ago.
I'm glad to read here that you have a chance at some reconciliation with your Dad. I didn't have the opportunity. I didn't necessarily want it and don't feel like I miss it, but I still think I would have been happy if it had happened. If that makes sense.
Anyway, I wish you the best with this GB.
ETA: Just read further and saw that he passed. I'm sorry to read that, condolences.