I killed everybody in The Fort and recued Benny. Says it's your choice whether or not you want him as your right hand man in ruling Vegas but you never get the choice. I can't find him in the tops or anything.

i think he just dispaears frm the game

That's what it seems like.

Whenever I tried rescuing Benny he used to bug and disappear halfway through the rescue. It's a pity they didn't follow this path through properly.