Crystal, You have to remember that j.w.'s treat every one that isn't a j.w. a follower of Satan.
My SIL, who is a j.w., hates me, too, and thinks I hate her. I don't, really, but I am upset with her because she drew my younger daughter into the cult. We talk to each other when we have to, and are pleasant with each other, but there is always a friction, and a sense of untrust between us, because she knows I am totally against her getting my daughter and son-in-law into the cult.
I'm no expert on advice, so I'll leave it to others, but it does seem to me that you are doing a great job keeping a handle on things, especially when it comes to your kids. Never trust your MIL alone with them. As soon as you do, she will work on them to try to turn them away from you, and what you are teaching them about life, and religion. I know it's hard, but just try to hang in there, and take advice from these people that have been there, done that.
Sorry to say, it's a neverending battle. Take a deep breath, and relax.
Try to cope with it. Wish I could give you better advice than that. (Thanks for the book offer. I might take you up on it).