Now what is wrong with this picture?

"The fact that my husband could care less (and my in-laws) about how I feel or that she is coming."

But of course! Why should he care, because:

"DH simply sits in his room and sleeps or hangs out in his "four walls" while i do all the cleaning, cooking and child care. Now I will have a fourth child who is also basically helpless (although for 89 she is remarkably healthy, she will not leave the house)."

EXCUSE me? YOU do all the work while HE not only helps you, but he "sits in his room" so he can blithely escape all the bedlam inflicted by HIS mother? Yes, it's kind and the right thing to do to treat his mother as you would your own, and care for her. As a Christian myself I couldn't agree more. But you don't have to shoulder an unfair burden while he does nothing.

Uh...I don't think so. If my wife EVER tried to pull such a stunt on me she'd never get away with it, because I'd never take it, and neither should you.

He has her over, HE has to share in the responsibility. None of this walling himself off and leaving you to do all the work. You need to be assertive and put your foot down. And if that's unthinkable, then you use the other options available to you.

1) LEAVE. No, I don't mean permanently! But temporarily. Pull the same crap on him that he's pulling on you. TAKE OFF. (Even Jesus made sure He got away from the crowds every so often - He didn't spend every spare moment tending His sheep). Go for a shopping trip, a walk, a ride....anything to take you out of the house. Grab your keys and your purse...and GO before he can do anything about it. Particularly on weekends. HIS time off will go towards caring for HIS mother. He wants to get the credit for being a good son and taking care of Mom...then HE'S got to do his share of the work...not foist it off on you. Just get out of there for a while, and don't leave him any choice in the matter. Let him fend for himself - and Mom - on his own for at least a reasonable part of the time.

2) In between times, when necessary and reasonable, YOU wall yourself up in YOUR room. If he can do it, so can you. Or better yet, at least a day or two a week, announce that "the kitchen is closed" and he will either be cooking or taking you and Mom OUT to dinner if he wants to eat anything that day. It's the least he can do after subjecting you to this degree of stress.

Be assertive. You have a right to.