I imagine that things will be different in a month and they won't feel I'm so wonderful anymore.
His family sounds pretty disordered themselves.
When my SILs met me, they hugged me and said "thank you for marrying him." The whole family was so relieved he had a built-in caretaker now who wasn't them. I should've fled, but just thought they were kind of over-doting. They actually were all pretty ok when I left him 7 years later, surprisingly - the main comment was "we can't believe you lasted as long as you did."
Different story, though, when I asked my son to move out when he was 18. He'd gotten into drugs, and had picked up his father's habit of ranting into my face and looming/towering to be physically intimidating. There's lots of OCD, depression and some OCPD and NPD in ex-h's family - pretty darn sure SaneSIL has OCPD, which tells you how disordered the rest of the family is, if I consider her the sane one! SaneSIL had always been very kind to me, including me in Christmas even after the divorce and remembering my birthdays. (CrazySIL was also kind, but is very ill and can't participate in relationships in anything like a normal way.) I was diagnosed with diabetes a few years before and take insulin. After the diagnosis, SaneSIL had consistently given me gifts like yoga paraphernalia and cookbooks, jewelry, etc. - all very thoughtful and personal. The year I kicked DS out, she was verbally very supportive, but sent me 5 pounds of chocolate from a corporate catalog for Christmas. I took it to work and gave it away, but have referred to it since then as the "festively wrapped box of anger and death."
Hang in there.