Give and Receicve! If he wants to be on the otherside of the equation then you must communicate with him why it is not happening.
Dominating in the 3sex is not something that I'd let continue there are three of you it takes longer for everyone to be satisfied and it can be an on going process of fun I see Wifey and Nik going at it even after I have reached orgasm when they are done I want more and nik watching me and Wifey after she has reached orgasm makes her want more...so on and so forth. So nip the all about me and my nuts crap in the bud soon.
As far as the separate sex in theory this seems to be something that should happen naturally but in reality it depends on the comfort level of all involved. In my triad we only have sex when it is the three of us. This way there is no one feeling like someone is getting something they are not. I know at some point we will evolve but I'm happy with the current status as of now. But you should discuss it with your partners to see if that is something that can be put into action.