Please just let him go now.

My Prayers go out to you and your mom. I myself has gone thru this . When my mom was terminal there was a group that helped me alot. It was called Hospice care. It is a group that will help you and your mom thru this time. It is a free system and I know they are all over the place. You can contact them and they really do help everyone deal with the process and they do understand.
Jim