You are going through one of the hardest things in life and it is compounded by H being taken over by an alien and you don't have him to lean on, which is what M is all about. Why they do this is hard to understand, but you have heard this many times, it is about him, not you. There is something missing internally within himself and until he finds it he is going to keep searching -- some men it is cars, toys, jobs, unfortunately his is an IA. I've seen it many times over the years here, the WAW finally comes to their senses and it is too late. Gardener is right, this is so far from easy, the emotions can take on ranges that one would not think even possible.
You are human. You are in a hard situation with the M and the death of BIL on top of that is makes it worse. You know what you can reasonably handle, if it is too much, get help, don't wait. Call me anytime, keep posting here. Come here this weekend, you can go to the funeral from here, don't be alone. Being with H is just like being alone, he isn't there for you, come be with people who love you, unconditionally.