I will refrain from trying to convince you that I know exactly where you are coming from as this would offer no solace to you. I want to express to you, however, that this is a dilemma that cannot be ignored. Somewhere within the depths of your soul, there is a submissive yearning for acknowledgement.
Contrastingly, your sub does not have a dominant yearning within him. And frankly, asking this lifestyle sub to "play" Dom may not ever work for him. Sounds to me like he is skirting the issue of Topping because he is wholly and completely submissive.
However, since you are the Dominant party, why not include another man into your scenes on occasion? Not necessarily even a Dom; just a hetero guy with a freaky side. Would your sub get turned on if he was chained to the floor and forced to watch as a capable man ravishes you?
This is a very tenuous situation that I am sure many of us can relate to, here. There are many variables, though one thing is certain: you cannot run from these desires forever.