I agree with your friend, she is absolutely right. You don't have to decide in the next 15 minutes. Start taking care of yourself and let him do what he feels is best for himself.
It is good that he is being proactive by seeing a doctor and giving his money to his mother to keep. However, it is not her job or yours to monitor how he spends it. It sounds like he really wants help, so, maybe give it a little more time and see what happens.
Although, if the years of lying is something you just cannot abide, then you must do what you feel the need to do. Do you feel you could never trust him again, even if he is able to go totally sober? A relationship without trust is no relationship at all. Hugs to you.