Maybe it will help to cope if you can throw some assumptions out the window. The assumption is often made that the ex will ride off into the sunset with the gorgeous new gf/bf into happiness and bliss.
Well, he is still an alcoholic right? So much for happiness and bliss because until sobriety is part of that glowing picture, the cruelty and verbal abuse will soon start with the new partner. The using and manipulation, the betrayal: it will all be repeated behavior. And of course, you know it won't happen quickly, it will emerge slowly, forming little cracks and chips in the relationship after a time, as it did with yours, and then the little cracks will turn into shattered pieces with more time. Sure, years maybe.The family, usually codependent and in denial, will hope beyond hope that he has changed, so of course they support the new endeavor.
The alcoholic will change jobs, partners, families, locations, hobbies, habits, whatever, in an attempt to escape that one thing that is inside of them that cannot be escaped: the alcoholism. The change cannot be made by any of these scene and costume changes: only complete sobriety will bring about any real change.
Maybe this isn't the best coping mechanism advice, but I think that the best recipe for happiness is the removal of unrealistic expectations from our views of reality. The part where you perceive their happiness as a realistic expectation is the part that hurts, but how realistic is that expectation?