There will be a time sweetie when your MIL will have other fish to fry and leave you alone. I am not sure how long you and you ExAH have been apart but it doesn't seem like it has been that long.
Time is on your side and I am told by a wonderful woman in my Al Anon group that you can choose to begin your day over again at any time. You can begin it again now and tomorrow is another day altogether.
I know how important it us to "re-write history" but I personally have never been able to do so. I also know how hard it is to delete an e-mail before I read it even though it would be a good idea. Us Al Anons find it difficult to do that. Healing takes time and you will heal as we all hopefully will.
I am hurting too and some days are better than others. The holidays were particularly tough.
hugs