OP I'm trying to think of a way to say this gently but... you dumping him in the heat of the moment was very imagine so you then saying to him you think you should talk "like adults" would have riled me so much.
Like you're allowed to be impulsive and childish when it suits you but then he should be forgiving and mature when it also suits you.
I think this needs to be a lesson for you. I don't want to make you feel more shit but you need to take accountability for this.
And if it really had been a healthy situation then he wouldn't have just stopped talking to you and not wanted to sort it. He's thought things over and agreed it should end. Respect his decision, which was (after all) your decision too!
The "like adults" comment is a very thinly veiled insinuation from you that he is being childish and as I said that would have been it for me!
Re stories on social media, I flick through mine all the time and you can't even tell who is going to be next up if you're scrolling through so you can read anything into it really.
The point is, if he wanted to be in touch he would be. If he wanted to talk, he'd reply. He hasn't and he doesn't.
You need to move on and also consider if you're (perhaps unknowingly) a little manipulative and used to being impulsive and people forgiving you.
I was a bit like that when I was younger and learned the hard way you can't make big statements like breaking up and then expect the other person to want to talk again just because you do.
Sorry OP I know it feels crap but it's done now and you need to move on.