i'm sorry for all this tumult DM.
you and your dh don't deserve it.
since you're not included anyway your family will have to decide what to do and how to do it. i know you want your mil taken care of but BY NO MEANS EVEN CONSIDER TAKING THIS RESPONSIBILITY ON YOURSELF.
it's too dangerous of a situation for her, and whoever has her in their home.
what is she turns on the stove and starts a fire. or escapes into the cold at nite? she needs to be watched. even if she needs some sedation to get her there.
sending prayers for your son that he will feel better and be tx'd.