The Jonathan that Jill writes in EP7 could really be Jonah from Interlude. Jill has thought of all of them. Ergo, this Jonathan is part of a group Jill knows. Jonah, Emma, Bret, and maybe Zoey. Jill said in EP5 so she would also vacation at the beach during spring break.
Jill is a person who doesn't care about rank and name, so it's also conceivable to me so that she would be friends with Jonah, Emma, Bret and Zoey. Jill won't be going alone though, she'll be going with your friends. Is that Jonah maybe really tattooing Olivia?
If that's the case, then maybe the MC has Zoey to thank for getting him accepted to college. Why? If Jill knows Zoey, Zoey will also have talked about her best friend and Zoey knows all about the MC, including his mother situation. Lynette knew the Royce family and so Jill will also know Lynette's family and she will know everything but one thing. What the MC looks like. Why this. When Emma sees the picture of the MC, Zoey reacts strangely and will not have shown the picture to anyone else.
The Royce's make sure the MC gets into college. But they are not sure if he is really Zoey's boyfriend. Jill and her friends test the MC because they don't know for sure if he is. They don't know what he looks like. That's why the concert. The MC plays with a strange guitar and he can play. The last test is Zoey herself, that's why she is at the party. She knows her best friend and all those who see it. From the Halloween photos, his grandparents also find out because these photos are shown publicly.