hi TheUncertainty! I don't have children so I won't even pretend to have a modicum of understanding of how one gets through what you are getting through. So I'll do what I do best - hope and pray the best for you and tell you that I care about what happens to you and your DS.
I Do have a difficult SIL. As I was telling a close friend today, I keep my SIL in front of me where I can keep at least one eye on her because I know she never really lets go of that knife she hides behind her back.