Close, but it's ことになる/なった. (The profile sometimes explains a future event.) する/した is used for the speaker's volitional action, as you wrote "decided to do something", but I don't think he wants to get a room in 問題児たちの巣窟.
Heh. He does make a habit of that, but at the time he's only focused on taking care of cats. Since you aren't allowed to keep cats in the regular dorm, they make him move.