May be he is just pretending.. you do the same talk one day & see if he ask you who are those people lol
Have you considered that he is faking being asleep and is trying to make you jealous?
he talks in his sleep. nothing wrong with that, and it's normal for a guy to wake up hard. just the natural order of things. I think you worry about something that is really nothing. just enjoy being with him, and forget about the talking in his sleep.
He can't help what he dreams. Not all dreams come from something in reality. If there's no hint of infidelity while he's awake then you might be acting a little silly.
He can't control what happens when he's asleep. I doubt it has anything to do with the level of pleasure he gets from you. Just like dreaming about monsters doesn't mean you really need to be concerned about monsters.
you probably do the same just not saying peoples names.
Ask him questions while he's asleep, he'll answer them!
Sounds like someone just might not be faithful...