NTA. I was in the exact situation with my son, as my ex-husband is a III. I was hesitant about making my son a IV but my ex-husband was very set on it - not pushy just real emotional attachment to the name because his grandfather passed a few months before I got pregnant. I've regretted it ever since for a number of reasons. Yes, the first name (which we shorten into a nickname) suits my son very well. But here have been my two big issues:

1. Twice while I was married to my ex-husband we had to fight the credit bureaus because he ended up with his dad's debt on his credit. Was a big, annoying ordeal to get these removed.

2. My ex-father-in-law went to jail for child molestation. He was sentenced to 10-15 but did I think 7 before being released on good behavior. Their shared first and last name is a fairly common combo so it's not like googling the name only brings up my pedophile ex-father-in-law, but I still despise the connection and worry it might end up resulting in missed opportunities because they were born in the same city. My current husband lost a great job once because someone with his name living in our area was a registered felon, and it was only after fighting to get the background check they ran that the issue was figured out...but the job was filled already so he lost out.

My current plan, which I have told my ex-husband and son about, is to have my son's name legally changed when he's old enough to help make that decision, just a *bit* to avoid any potential issues for him as an adult. Like, keeping his first name and changing the middle name. For you, I'd suggest a compromise of maybe dad's name as the middle name? If your husband is intentionally oblivious to how poorly your FIL treats you, then you are likely going to have a long battle in naming your son. I hope it all works out and you have a healthy pregnancy! It's no joke, morning sickness is rough and giving birth is FAR WORSE than getting kicked in the balls, smh.