After all is said and done, and while you're sincerely trying to look out for MIL, the bottom line here is who your priorities are, need to be, should be.
And it doesn't take a rocket scientist to figure that one out. Your UTMOST priority is your family. YOUR WIFE, AND BABY!!
That's it!! NO ONE ELSE outside of yourself. NO ONE!!! How far should you take this?
(ok, I'm not good at illustrations but you're get it as you read):

If you, your MIL, your wife and baby were on a boat, it looks like it will capsize or something, but you can only save two people, not including yourself, who would it be? No, as you're reading this, and actually as I'm writing this, I can't imagine such an emotional momeny. Yet, who-would-it-be?
YOUR WIFE, AND YOUR BABY! THEY are your immediate concern!!!! No one else!