I too am the mom of a compulsive gambler. My son is 28 and this started 10 years ago.
I wish I could give you some great words of advice that would make this all go away… unfortunately such words do not exist. As you have said “it has to come from him”. Sometimes, however, when we get support and help for ourselves and refuse to be a part of the chaos that the gambling creates things start to move in a positive direction. We start to feel that we have some control over our own lives.
Keep writing/venting on the forum, read as much as you can on addiction and face to face support with Gam Anon will all help you find better ways to cope.
As Velvet says your son can learn to manage this addiction and live a decent life. .. it just has to be his decision that he has had enough.
Cathyx