I am sorry you are going through this.
Some ideas you could consider doing... YMMV.
1) Check your own laws. You are responsible for your own emergency preparedness. If you do not have it already, create the things you need to provide for the child if you or dad get run over by a bus somehow. Have that stuff in order.
2) Know Mom would have to cross state lines AND that no judge wants to set a precedent for taking a healthy baby away from a healthy mother. It's in your favor unless she has more than "I don't like their sex life" evidence.
3) Document her threats and notorize it. (ex: print emails, save letters, get cel phone call logs, etc.) Put in safety deposit box.
4) Tell her to cease and desist harassment in a documentable way. You may not be at "lawyer level formal letter" -- certified mail might do depending on the "volume" of the threat. Document anyway. She keeps up, document AGAIN... maybe that time with a lawyer letter.
5) Cut off all contact. No sharing pictures, letters, visits with the kids or you. The less info she has to use against you as ammo the better. Disentangle self from your mom if you have entanglements beyond emotional. (ex: financial, shared property, etc.) Then she can't use those to control you either.
6) Do not put kid in a position where Grandma can swipe the kid. No babysitting!
7) If you mother gets over herself and you want to rebuild trust there, do it slowly. Before you do, if she's a controlling mom type, learn the tactics so you can recognize them if she
swaps tactics and tries a new one on ya. (I'm guess sections 8 & 9 right now.)
8) If you recently came out to her, and you think she's doing "stages of grief" for the loss of knowing you as X and now having to deal with you as Y and taking her angry stage out on you --
know the stages of grief. And don't lift a finger. Let her sit with her grief. If she asks for APPROPRIATE help, that is one thing. INAPPROPRIATE moves like threatening to take your kid from you, that's for crap. Expect to be treated BETTER. Be cautious that "sob story, poor lil' ol me" is sometimes a control tactic.
9) Remember you don't have to accept every invitation to Crazy Town that comes to your door. You can RSVP "No thank you."
10) Remember to BREATHE. You can make your own adult decisions and deal with the adult consequences. If you need more support during a tumultuous time, get a counselor, see your minister, BOTH. Whatever it is you have to hand.
Get a general doc appt too. Esp if you are stressy and struggle with sleep -- see what can be done.
Get the kid an appt with their doc. Quietly have a word with the doc outside the kid's hearing that you want the kid checked for abuse. Because your mom is threatening you that you/spouse are abusing the kid and you are NOT. There. Doc appt on the record...
should you ever need it to show that your kid is fine and to show that when things came up you do the responsible parent things to do.
11) TELL some other trusted relatives/friends what's going on. Then it is "old news" to them and you have them for character witnesses if ever needed. "Yep. Mom been harassing her for AGES on this and the kids are all fine. I've known this has been afoot since _____. " If the children are school age -- tell the principal/teacher, pref in writing with copies for you AND in person. And if for some reason your Mom is on their school papers as an "emergency pick up" person take it OFF. Put Mom as a "Do not release my kid to this person" instead. Ditto to whatever other teacher people they have -- sunday school, boy scouts, tennis, whatever.
Which is more documentation with/from OTHER people that it is your MOM causing you wacko. It's not just (she said - she said) stuff. Stick it in the safety deposit box.
Don't tell mom you do it either. Just... quietly build your ace in the hole and store it. It's not "fun" to talk about or deal with but silence only helps the one that is threatening. It doesn't help YOU.
So pick who your safeword people are and
then sing like a canary to them! Hopefully mom's just acting out and needs time to digest this new reality and will get over herself and apologize.
But if it ever HAS to get to lawyers and a custody case, now you have a folder of tools your lawyer can try to WORK WITH rather than a big ol' empty folder of nothing.
Hope for the best, while preparing for the worst.
Your first loyalty now that you are a parent is to YOUR child. Not your own parent.
My 2 cents,
Galagirl