Tom is in a very similar position that Jackie was at the end of season. Except even worse.
Like Jackie he became aware that someone has a crush on his significant other. And that someone is his so's best friend.
Except he knows she reciprocated those feelings at ine point and still might. And that they acted on those feelings behind his back. Ans that his rival is also his only friend.
Actually scratch that, he's way worse than Jackie ever was. I don't see how Tom can get out of this situation with any self respect left im tact. Either he stays with Star and accepts he was cheated on and also accepts that Star will live with somone she's in love with who isn't him. Or he accepts straight rejection for a second time drom the same girl.
I think they're trying to mitigate the damage to Tom's pride by making his friendship with Marco stronger. As if that will make his dilemma less painful.