Step grandparents? Need advice

So my mom moved me (all the way across the country) in with her boyfriend immediately after she divorced my dad.. (my dad was extremely abusive, not bitter about the divorce, it needed to happen) anyways, I was almost 16. My mom constantly pushed me to get me to hang out with him and be cool with him. She never tried getting me to call him dad or anything but I was pissed she made me leave my whole life where I was raised and that she forced a stranger into my life (they were “high school sweethearts” 🙄). Anyway, I didn’t even care to be civil with my moms new husband until like 3 or 4 years later. I basically just ignored him and avoided being around him. I met my now husband when I was 17, we had our son at 21. My mom immediately called her husband his pawpaw. She knows that my dad is in my life obviously and that my son will call him grandpa or whatever but she immediately assumed I’d just be chill with her husband being called pawpaw, and I’m definitely not. My son is now 16 months old, and I haven’t brought it up to her because she’s not someone to ever admit she’s wrong in a situation and she can’t just have a conversation, it turns into an argument. I haven’t pushed to discuss it because my son doesn’t even say pawpaw but me and my husband have full intention on not raising him to call my step dad that. Any advice on how to handle this? For the record: I understand some people are cool with their kids calling their step parents grandma or grandpa, I’m putting it out there now that I’m not because of my particular situation. I don’t see him as a father figure at all. He’s never raised me in any sort of way, he’s always just been there, has never been a significant part of anything important in my life. I simply see him as my moms husband. Also, I’ve grown up with a very split, divided, complicated family dynamic. I really just want my son to know who his 2 sets of grandma and grandpa are, not all these married in random people. My dad jumps from woman to woman a lot, the women in his life go by their first name, if I even let them around my son because I don’t want him confused. It’s also important for me to get advice on this because we’re due with a daughter in February and I don’t want my mom continuing to refer to him as pawpaw. Thanks in advance 🙂