Best friend becoming toxic?

I have had this friend for 20 years who has always been there for me. The past few months I have been debating and evaluating our friendship. First of all he has gained about 100 pounds and refuses to do anything about it. I have tried to help and be supportive to no avail. I am also pretty sure he is bilolar but refuses to take any "psychotropics". He wont even see a therapist. I have come a long way. Im successfully clean/sober, going back to school, helping my kids. He lives in the past. "if I had stayed in the military..." I hear this at least once a week. Also "if I won the lottery.." It is getting increasingly Difficult to be around him. He gets mad half the time if i make plans without him or have someone else drive me somewhere. ( I clean his moms house for 1/4 of what it would normally cost. I have overcome alcoholism, depression, and my bipolar disorder is managed. I dont want to END the friendship but I dont knowwhat else to do. How can I set some boundaries??