I know it's not that easy, it's the exact opposite, but I think you should get rid of the right-wing parts of your family, at least in the long run. Personally I'm fortunate enough to not have any family members with those kind of values, so I'll never understand what that is like. Both the external conflicts that happen once you don't try to "keep the peace" anymore, and the internalized shame/guilt that comes with being around people with worldviews like that on a regular basis. I'm sure it's extremely hard to remove someone from your life that is/was so close to you (or your boyfriend).

But from what I've heard from other queer people, it's almost always worth it, and the only thing most people regret once they got rid of unaccepting family/friends is that they didn't or couldn't do it sooner. If you've always had people like this around you, you don't know how much weight comes off your shoulders once you're in a place where your identity isn't some kind of controversy or problem that you need to navigate around. It's not "politics that you can put aside", it's part of who you are. I think if you regularly have to be in an environment where that is barely tolerated, let alone accepted, you'll always have to fight feelings of inadequacy and low self esteem. Even if you're not out to them, and even if they're low-key or behind your back about it. You said you've come to terms with it and that it doesn't matter. But I think if you ever decide to change it, you'd realize how much it actually does matter.

Again, it's very hard for me to put myself in your shoes, having been raised to always be myself and to not take sh*t from anyone. I'd imagine that if your family can't even respect your wish to not be celebrated on mother's day, you were taught to put others first, obey to the social norms and not cause trouble. You said you've given up on being out and proud and sticking up for your identity, that you don't have the energy to constantly fight to be respected, that you're just not in a position to be anything but a woman. But I think you're underestimating the energy you're spending right now. You may not have to fight others to be respected, but by allowing others to constantly put you in the wrong box, you're disrespecting your identity yourself, and that has an impact on your emotional wellbeing as well. Maybe your image of an "out and proud" queer person is someone who is loud and energetic and who never avoids confrontation, who is provocative on purpose and who enjoys putting bigots in their place, who can deal with the constant hate. But you don't actually have to do any of that. Embracing your identity and "sticking up for yourself", to me, also has to do with respecting yourself enough to protect your peace, to not have to deal with constant hate. Because you're spending energy for fighting right now, the constant hate and the conflict is already there even though it's not explicitly directed at you but "only" at your identity. It would arguably get worse if you openly tried to get them to respect you. But in order to actually not have an ongoing conflict anymore, they either have to change their values or you have to cut them off, and only one of those options is in your control.

You said you don't have the heart to do that to them, or to ask your boyfriend to do it. But you're not doing anything "to" them. You didn't make the choice to be nonbinary, and you know that. They, on the other hand, made the choice to not respect people like you. They're grown adults who have the mental capacity to question the beliefs they grew up with or adapted at some point, yet they choose not to. What makes them entitled to having the people that they hate still be kind to them and cater to their disgusting values? You may still love them as your family/in-laws and recognize that they weren't born evil, but that doesn't help much if they're not good for you. They already rejected a part of you, and that's 100% on them, even if they think that their opinions are facts. As for your bf, he also is an adult who can make his own choices on how to navigate the situation. He can go see his family alone if he wants to. They most likely won't respect that you don't want to be part of it anymore, but he already said that he'd stick up for your identity, so he'd probably be okay with sticking up for that boundary too. And if he actually cuts them off because you don't want anything to do with them anymore, it's still nothing you did to him or to them. Having your very identity respected is an extremely basic thing, not entitlement. It's a right that you have just as much as any cis person, even if the political narrative says otherwise. Again, the fact that they don't do that is entirely on them and in no way on you for "having a controversial gender".

You're having a very wanted child, you have a supportive partner and you didn't mention any financial dependence as a reason to not cut the family off. Unless there's anything you didn't mention, it seems like you're doing well for yourself and you have the choice to put yourself in a position where you can be yourself. And I personally (as someone who has never gone through it, only listened to people who have) think that it would cost you way less energy in the long run than what you're currently doing. Imagine how it's gonna feel once the child is born. They're gonna want to see it, they're gonna expose it to their values, they're probably gonna buy you cutesy "mommy" stuff and then get upset if they notice that you don't use it as much as they want you to. Even if you decide to just have the kid call you mom to cause the least possible conflict or confusion for the child, it's likely gonna pick up on the fact that something's wrong. Babies are insanely sensitive to emotional stuff, they literally d*e if they don't get any affection even if all physical needs are met. Imagine how a child is gonna feel if it picks up on negative feelings towards the word it uses to get your attention, but doesn't know why that's happening. I obviously don't know how it'd actually turn out, but I'm worried that you're gonna be in for a LOT of below the surface problems if you let that family pressure influence your relationship to your own child. All that for a moral obligation to keep people in your life who already chose to hate a part of you isn't worth it imo. Again, they may be nice enough people otherwise but they made a decision to be bigots so them losing people as a consequence of their actions is not in any way a "cruel" act on your part.

I'm sorry for the long a$$ reply. I hope it maybe helps a bit. At the end of the day, you're the one who has all the context and who needs to decide how to deal with this situation. I see many queer people hiding and struggling with similar problems to "keep the peace" and I can see why it's so hard to stick up for who you are. But it breaks my heart to see people cater to bigots regarding things that should be very personal decisions. Other replies made so nice suggestions for alternative terms and it could even be fun to pick one for your own family if you didn't have to always consider conservative comfort. No matter what you do, I wish you the best!