Most Helpful Guy
Trust issues obviously but I would ask, does he have legitimate reason to distrust? Social media is the cause of many problems and so are friends buzzing in his or your ears. But in all seriousness, if either of you are concerned with what's being said or posted by others that might indicate you two aren't ready for a relationship.
Most Helpful Girl
He's clearly still into you and wants to get your attention and speak to him. I don't know if it's petty, since it's pretty common for ex's to do things like this. I think you should just ignore him as much as you can though. If he talks to you just be civil and polite but keep ignoring his posts like you've been doing so far.