Do you like this guy enough to date him even if he doesn’t change this behavior? Movies tell us that we can change people, but we can’t, we can support and help them, but they have to want to change.

I’m not sure if when you say look at pretty people on the internet if you mean like sexually explicit pictures/videos. If that’s the case, depending on how long that’s been a thing for him, it might not go away. Pornography addiction is a real thing, and it’s hard to break away from.

Since you guys are not dating, he is still within his rights to look at people on the internet. If you like him and want to date him, you could talk to him about how you like him and want to date him, but that him looking at other women on Instagram would be upsetting to you, and that you would want him to not do that while you guys are together.