oh, i can relate very much to these difficulties! my husband and i sought couples therapy as a result, and if there is tension between you and your spouse as a result, i would highly recommend this route.
the book, "Boundaries: when to say yes, when to say no, and when to take control of you life" by Townsend and Cloud. This is validating but moreover outlines how to set and stand by boundaries so that you do not go crazy.
This book was VERY helpful to myself and my husband. I have in-laws very similar to yours it sounds like, and for us the end result is that we are moving to the west coast in 6 months. it seems like part of the problem is that my in-laws have not let go of my husband as a son; they do not realize that we are a fully other family now and need to be treated with that space and respect.
Putting space there is a great idea, if even temporary. This can help them to understand that you are serious, that you will have a relationship with your boundaries respected, or not at all. Also, you can expect that when you do set a boundary, they will push back twice as hard, atleast for a time. It sounds like a great idea.