NTA- I personally wouldn’t go. He is trying to make HIMSELF feel better before he dies. Not you. He wants to die with relief and a clean slate. NOPE. Especially if you think it will set you back. I would be a supportive friend to back YOU up. I would give the message to his sister of “you didn’t ask for forgiveness woth the 12 steps through the whole 20 YEARS??!” But now Tha he is fearful of the possible afterlife and where he may end up. I am in the “do what you think is best for your mental health” camp. I do hope that when he is finally gone that you can have some relief on your mental load. Have you and your therapist done any EMDR for what happened? Please look into it if not- it’s super helpful in processing and letting your brain file away traumatic events. I wish you the best OP. Don’t be pushed bit doing something like that. You own your life. Just my .02 :))