It sounds like she has been uncomfortable with you and your behavior for awhile before this incident. Did you really never pick up on that?

That alone suggests you aren't as aware socially as you could be.

Evaluate how you got to a place where you didn't notice this was a growing problem. Honestly, drunk texting a man in a relationship late at night, being overly friendly with him and not with his wife, etc. aside the fact that you felt like it was okay to instagram their baby is deeply concerning/ that alone is a huge faux pas if you didn't ask their permission. There are a lot of things here that really make me think you are behaving inappropriately in multiple areas without realizing it. The fact that you continued to text him about it afterwards is also concerning. She handled it badly, but it has obviously been brewing for awhile and you didn't realize (which makes me think the accusation that you ignore and don't pay attention to her is correct). How do you actually go this long without realizing that someone dislikes you or believes you are trying to cause trouble in their marriage when you've been at their family gatherings and holidays? That's really something you should have picked up on and since you didn't, it is pretty easy to assume you've been ignoring other social cues or crossing other boundaries without realizing it.

Reach out to her directly. Not him. The fact that you've already reached out to him is bad. The fact that he has ignored you is going to make it look worse if you reach out in a few weeks (because it looks like you aren't trying to repair things out of concern for her).

You need to work on how you handle yourself socially or this stuff is going to keep happening to you.