Oh dear, why on earth did you marry a jw in the first place? I grew up in a divided household and it was miserable, especially at Christmas! I actually dreaded Christmas, it was an intensely unhappy time of year in my home. I would never be able to put my kids through that hell. I hope if you ever have kids together you make it clear that they arent going to be indoctrinated and forced to sit bored shitless in the KH, dressed like little used car sellers.... Still, love is blind I suppose...(and stupid-I know that from personal experience).
You could always be unbelievably generous to your MIL by taking her into the woods and shooting her in the chest several times with a large calibre rife(or shotgun if you prefer). That way you would be able to have a bit more peace, and she would be in a state of blissful non-suffering, just waiting for Jehovah to get his groove on and raise her up. A much better position to be in than all the other countless millions of decent, good-hearted people(like you) who will be destroyed for eternity, simply because they happen to be alive at the time Armageddon takes place...Do her a loving favour, pop some caps in her old ass!