but it's not clear why he's doing it or who he's working for.
He's not connected to Vinnie or Burke.
The only explanation is that he wants to be president of the fraternity and feels unappreciated all the time, she has envy for everyone else, especially MC.
Its just a theory, it could be completely wrong, but what made my spider senses tingle its the fact that he has no flaw, he is always the cool one, he is more bro to MC than Derek the bro archetype, he warns you about fucking Sage at the party, he selflessly offers to work at the Retirement Home, etc, at least Derek has his big mouth as weakness, Jacob has none. Of the top of my head, the only 'flaw' he has in the story its in ep7 at the HOTs party when he is a coward and stays upstairs and avoids the alphas, unless that is by design and he didn't want to mess with them in the first place.

John Boy would have been a suspect as well, for being too perfect of a character, always cool and wise, but he is so detached to everything happening and he is almost never there unlike Jacob, that legit will be out of the blue if he would be revealed as the mole.
Jacob has the reason, he got arrested and humiliated during hell week, I don't know how strong of a villain origin story that is, but at least there is something to work with compared to everyone else.
Anyway this all hinges on the hypothesis that the mole
exists and
everything is done on their own accord and not a blackmail, or manipulation proxy, like lets say Dani using Jam Jam's phone/laptop, or literally anyone in the DIKS being blackmailed.