I think it’s a nice gesture to share your concerns about your adult son with your ex. The outcome of that is going to be whatever it is. When I shared my concern to my ex about our adult son and his drinking my ex was defensive and condescending. He had to discover and see it for himself.
Hope is not always gone even when we feel like it is. I had to ask my son to leave the house due to his excessive drinking. It changed our relationship for a couple of years but then all on his own he realized how drinking was affecting his life and he took steps to change that. He is coming up on almost 2 years of sobriety and our relationship is pretty terrific.
No, you are not alone and I certainly can relate to loving a son but not wanting to be around them.