How can this issue regarding a search for a sub-leaser be resolved, or helped?

I’m going to try to make this short because I need help urgently.

I live in a 3 bedroom apartment. Until a week ago, I lived in one room, my boyfriend (who I used to share a room with but is now my ex), lived in the other, and we had a 3rd roommate. Me and the 3rd roommate Joe are still in place but my boyfriend, upon returning to the states from a month and a half long trip abroad, decided he was going to move back to new jersey and move in with his mother. So, he’s looking for someone to sublet his room. No big deal, right?

Well here’s the thing. It’s a college town and I don’t want some brainless dope as a roommate. Still normal, right? My ex is in a huge rush to find someone by the end of the month so he doesn’t have to pay any more rent, but he’s only found one person who is still in contact with us and didn’t flake out. This kid seems like the biggest dope…I told him I was from Pennsylvania and he said “Wait where is that?” REALLY? IF THERES ONE THING I HATE ITS A LACK OF COMMON SENSE. He also only has a job because his mom got him one. What? The upsetting part is that my ex knows this but is being a big DICK about it and trying to tell me it’s not a big deal, and he should just move in anyhow. I also know that he’s only saying this because he doesn’t have to live with the idiot. I’m not letting him move in, that’s that, but the bickering and arguing and him trying to tell me I’m wrong is really becoming problematic. IIIII have to live with this person, should I not be able to be choosy? It’s not my fault he waited til 5 days before the month was over to come back and suddenly try to find someone who’s a good fit.

Am I right or am I right? Is there any way to resolve this? Let me reiterrate that I fucking hate stupid people. Stupid people also tend to be brainlessly messy, and I don’t wanna fucking clean up after another roommate all the time.

iNPUT, PLEASE?!