Am I being too paranoid?

My fiancée does private security.

He was married once before to a woman who he was with for seven years and then was married to for two years. Recently, she got a new job as an apartment complex manager. As it turns out, that complex employs his security company.

He has made calls because he wants to get transferred to her complex, as she will be moving in there. When we first go together, he broke up with me because he "was still in love with [his] ex". We eventually reconciled and moved past it.

They have 2 kids together and a court ordered custody agreement in place. I get he wants to watch out for his kids, but it concerns me that he's trying to be so involved in her life. Also, He doesn't understand why I don't want to be friends with his ex. I'm civil, certainly, but I don't want to hang out and grab beers after work or anything.

He would literally drop anything to run and help her. Not the kids, but her.

Am I being too paranoid? Should I be worried? Do I even have a right to be? He doesn't listen when I try to express that this makes me uncomfortable: him working side-by-side with his ex in a professional setting. Also, she is the jealous type.

Any advice would be appreciated! Thanks!