Unless you have a promissory note signed by your MIL for the funds you put out to bring her mortgage current I think you should regard the monies you put out as either a gift or rent. Retribution will not help your relationship with your MIL or your wife and it won't even help your piece of mind and it definitely won't get you your money back. Revenge feels good until the fallout. If you're that financially stable I see no reason to stay at your MIL house and perhaps your wife (and you) should consider some counseling to work out dependency and boundary issues.
Oh, I see your wife is ready to go? Then leave already and get out from under your MIL's thumb.
Last bit then I'm leaving this thread. If you don't want advice about private matters then dont bring it to a message board. You invited folks to make comments about your private affair/mess. No one here solicited any information from you. You did that.