One time I got myself hooked into the claws of a sex addict. Addiction is addiction Aly, they are all the same though their dishes are different. My relationship mimicked the description of yours - we met and fireworks exploded. No more a perfect man for me had every existed. I found out about 2 or 3 months in what I was dealing with somewhat by accident. I believed him when he said I had CURED him. I believed everything he said while I sunk in the quicksand, and by the end of it a year and a half later he dumped me like I was a piece of trash on the floor of his car. By that time I didn't even resemble the person who met him, nor did he resemble the person who I fell in love with. I turned on myself for being a crying, whining, nag - weak. I looked for reasons to contact him, I obsessed over him, I cried endlessly, I called into work so I could sit at home and figure out how to get him back. I looked like hell. I didn't want to go anywhere unless it was with someone who was willing to talk about him and what he had done, and give me hope that our true love would conquer all (and they were becoming few people).
If I listed all the horrible things this man did or said my post would be 3 pages long. Yet I was willing to excuse the behavior to get back to the days when everything was wonderful, and he made me feel we would conquer the world. How sick is that and do you see that it is I who became the addict also? Do you see this behavior in yourself?
I did find out that he had his hooks in someone else (well, to be truthful there were many). She wasn't very attractive, and I obsessed over her and why he would be with her when he could be with me who was so much better. What I realized is that the person and whom they were with didn't really matter - he collected people similar to the way people collect shells on a beach. The natural progression of a relationship is for it to get deeper and more serious. At that point it would begin to hinder his addiction and the days were numbered. While he tried away to figure out how to keep me and continue screwing everything that moved, I was trying to figure out how to make him stop and end up with him.
I was with him for 18 months, 5 were good, 13 were horrific. Then I let him have 6 more of me while I cried and fell apart and he moved on as if I and "our love" had never existed. Guess what? Our love really never did exist. It was an obsession.
My healing began when I forgave myself for allowing him to treat me like dog sh!t on the bottom of his shoe. His actions were unforgivable, atrocious. And that was the man I wanted.......Really??? I wanted to marry him can you imagine? Saying I dodged a bullet really doesn't capture it. My advice is to start forgiving yourself for getting involved, ignoring red flags, accepting unacceptable behavior. You should of kicked him to the curb a myriad of times and you didn't. Its ok, you made a mistake. Next, start taking care of you. While you are there in Vegas don't sit in your hotel room lamenting over the alcoholic. Get out, go for a walk, Have a nice dinner, go to the spa. Go shopping, ride the ferris wheel, go see the fountain show at Bellagio. Stop handing over anymore of your life to this man. You will be surprised at how quickly the fog will lift when you put yourself first.
In all liklihood lurking below your Ex's addiction is a personality disorder or mental issue. Its very common. Likely there is much more here to deal with than you can imagine. As for the mother - you became close because you were her's sons savior and full time babysitter. The parents will generally always side with their kids, she is a classic enabler and codie and will most likely support ANYONE who is willing to step up and take the position of full-time handler (so SHE doesn't have to). She is a big part of the problem and in no way the solution, she was not your friend. had she been you would still be in contact and she would tell you to save yourself and forget her loser son.
You will get over this.