I think you're setting yourself up to fail here, and him as well. He's lying to you and hiding it from you, but why? Are you making it difficult for him to be honest with you? In his mind, he could be doing something that is a very normal outlet that many, many people also find perfectly normal, but you don't so he is banned from looking at any kind of porn unless it is specifically with you, even in private, on his private phone and it is not affecting you in any way.
That just seems overkill to me. If he was paying for porn and it was hurting you financially, I could see it. If he was addicted to porn, getting freaky or he was no longer interested in having sex with you over it, I could see the problem. If he was spending all of his free time holed up in front of the computer looking at or watching porn instead of spending any time with you, going to work, spending time with the kiddo, doing other things, etc., I could see the problem. Even if your bedroom floor had turned into a wet sock graveyard of shame, I could see it.
But the guy has a couple of porn sites and pics on his phone (um, because he obviously can't have it on any shared device or at home because you snoop through his stuff and don't trust him - side eye). I don't think that's a big deal. And if it is such a huge deal to you, you probably shouldn't have married the guy. And he shouldn't have married you.
When I was younger my boyfriend watching porn really bothered me. I've grown out of that insecurity, thank god, and understand that him watching porn is not a reflection on me.
Just my opinion, but I think you will be a lot happier if you ease up and let this go. What else are you going to do? Divorce over this?