First, I am glad to see you try Naltrexone - I have been mentioning it frequently here for others who might not understand that there is medication that helps with the urges and cravings. I asked you first about your coping, because it is proving to be successful, yet still not adopted by many physicians.
If anyone is looking over our shoulder, and thinking they might have a problem coping with the urges, I hope they take your experience with Naltrexone - right?
As for your history of drinking, I don't want to dismiss it entirely, but there certainly is not much the mother can do about it with regard to Custody. She left the children in your care while knowing you have had issues in the past, so she is equally guilty of using bad judgement with regard to protecting the children.
If the situation was reversed, and you were here telling us the mother has these issues with drinking, we would not be focused on that as a tactic to obtain custody. The bottom line is really what kind of a parent you are, not how horrible the other parent is. Does that make sense?
Volenti non fit injuria