You're 30 years old - I think you should grow up. What's the big deal? and you say you're working for him? Well maybe you could find your own place then. He deserves a life just like you do. To be blunt you need to get over it. It's really not for you to say how old the lady is that he should be hanging out with. And who cares if it's only for sex? Then you won't have a Stepmom!
Hang in there. I understand the immaturity cause I'm immature about everything.