This is SO awesome to hear!! Doing this as a team supporting each other will make it easier. I wanted to comment on the original but I was having major anxiety over it cuz I couldn't say what I felt the need to say without sounding like a heartless bitch. My mom was a pro-level narc abuser & some things you said totally struck a chord.
•>"just figuring out what we get a say in".
•>"she will only take the baby away from me....".
•>"will take him out of my arms when I go to feed".
•>"wait until I left my son there for the wknd & change it".
•>"blatantly ignore my directives" (this is the big one).
This is some Jedi level abuse & you're 100% correct they'll never change. That last one is what hit me hard: she's an legit dangerous threat to your sons safety & well being. No exaggerations, laying him on his stomach & leaving choke items is potentially fatal & she is unable to stop. I may sound dramatic but my mom was exactly same. Made me crazy...till the day she pulled up with my 15m DD in the car without a car seat or any restraint at all. I freaked, she blew me off cuz I was making up BS for a fight & she hasn't used one yet & babys okay, duh. I realized that psycho was a danger & may have loved DD but would never put her needs 2nd or be wrong, she's never been alone again.
I had great support from hubs & it was still insanely hard. My best advice is don't think you can guess how they'll fight back, be ready for things you can't fathom. Also, do what you need to stop seeing them as grandparents/family/etc. They're worthless titles & don't come with abuse options. It's the excuse that made me break my own rules, she wasn't capable of the feelings & boundaries that were universal to other humans.
Be patient with hubs & make sure it goes both ways. You guys are gonna do great! Good luck!!