Good morning. What a refreshing change it is to read your message. We will never ever hear anything like this from our daughter-in-law. If it were me, an apology and a different approach would make me/my husband forget all the spite and manipulation.
They say a son is a son till he gets him a wife, which I've always taken to be appropriate in our case, but even that has been used against us as proving that we are at fault. Actually, it can be read both ways, sadly. More ammunition.
We know of at least 7 couples in our close circle of friends and family who have similar problems to ours. The spite and malice are so hard to bear, with many sleepless nights. I have lost count of the number of times we've been hauled over the coals about something we seem to have done and yet we wouldn't dare return the challenge because, afterall, we love our son. Don't like him much though now. We don't want to lose our grandchildren.
Do it. You needn't get down on your knees. A simple apology and a new start would, if your mother-in-law feels anything like we do, immediately lift her spirits. I see a whole new relationship ahead of you.