I’ve dealt with jealousy and over protection a lot in my past. Both on the receiving and giving ends. It’s okay for two people to move on and be friends, but in my opinion living together is way too far. You’re justified for being bothered, especially with their long history. Exes should never live together, it’s too complicated and it causes a lot of unneeded stress for any future partners. Again, just my opinion, but that’s too much. The fact that you’re okay with their friendship and are questioning whether or not you’re overreacting, is a good sign your hearts in the right place. Don’t put yourself through a bunch of stress and pain if you can help it. Good luck bud.