I lost somone to a rare cancer with almost zero chance of survival. A treatment with 65% success was available 30 days after they died. Ill always wonder if things could have been different. Maybe if we looked harder for trials but like you we thought it a hopeless waste of the limited time left.
I’m sorry for your loss. Words from an internet rando don’t mean much, but you did the best that you could so don’t worry about what ifs. Do your best right now.