Holy shit, just rtft.
Firstly, a massive YANBU!
Secondly, grammar and punctuation nazis can fuck off, way to ignore the issue and make OP feel like shite.
OP, I completely get where you are coming from. Your pregnancy, you get to announce it. Your uterus, you get to share pics of it. Your baby, you get to say (until she can do it herself) who gets to own pictures of her. All of that is destroyed when you have selfish people like FIL doing what they want.
I learnt my lesson about Facebook the hard way. I announced I was in labour with DD1 before I went into hospital, prompting loads of texts and messages. DD1 died. That announcement made my life needlessly difficult at a horrendous time. I left FB shortly after.
With DS1, we only told family early, never put it on the internet, and announced in person to friends at 23 weeks. Feel free to tell me how fucking precious I was. We only rejoined Facebook after he arrived safely, and only announced his (early) birth once we were home from the hospital. Now, we put the occasional photo of us up as a family, have very strict privacy settings, and don't tag him or us.
The fact that FIL is completely disrespecting you and DH is the worst thing, and I would take him at his word and leave him alone. Announcing your pregnancy at 8 weeks is appalling, as are his comments in response to you asking him to cease his FB activities. You are completely justified in not wanting pics of your baby to be out on the internet FOREVER for anyone to copy, search and use as they will.
I know mothers who have had photos of their angel babies stolen and used by trolls, there are babies used for memes, and if you don't want to risk that, it's your right!
I'm shocked by the response you have received on this thread, and don't think you are PFB at all. Once again, YANBU.