I think Jason and Iikka would get along well. They've both put up with shit from other people, and from shitty parents. Obviously Iikka is much more aggressive and Jason would have to get him to step back and cool down sometimes. Jason's goal would be to prevent his friend from ending up going to juvie or worse.

Just throwing out opinions:

Mario strikes me as an all-around good guy that would get along with anyone easily, and be a good "glue" for the group. I think it's the scouts thing. Seems like everyone would know that guy.

Max's life experiences are so positive they would seem surreal to Jason. He'd feel awkward admitting his life circumstances around her. She'd have to try to get past a wall.

Olivia is smart, and kind of bitchy. He could handle that, as his own grades are pretty ok, and he's used to bitchy/smartass women from his mother and her friends. Her book smarts would match his work ethic and street smarts. He could let things roll off his back coming from her that others might be offended by.