welcome, apart. I am so sorry to hear of the loss of your A. A year and a half ago, I lost a friend of 25 years to the disease. He was aware of his self-destruction and it was so painful to watch. Many of us tried so many things - they must have added up to 1,000 different pleas. Sadly, none made any difference.
I have come to accept that there truly was nothing anyone could have done to save him - he had to do that himself. I hope as time passes you will have some peace with that. Grief counseling could help - have you looked into that.
Please keep coming back and posting; many here have been through it and you don't have to face it alone.
Much love.