Hi truckinnhorsin, welcome to the forums
i confess i don't have any experience of the question you ask, but one thought that immediately came to mind when i read it was something on an old, old thread when someone asked about female dommes and male subs. i won't bore you with the detail of it, but what became apparent and a point on which most people agreed was that submission and dominance wasn't about wrestling someone physically to the ground, tying them up whilst they continued to fight etc. Sure, those things can be fun, but it isn't where Ds really lies, IMO. 'What of it?', i hear you ask..well, i'd say this fact went in your favour and what i'm trying to say is that your partners infirmity shouldn't interfere with your level of submission. Make sense?
i see that pratically, his condition could be limiting, but there could be some ways round that. Being dominant in a scene doesn't have to be about doing intricate and difficult bondage and marching around with a whip....certainly in my experience, there's nothing wrong with you lying on a bed and him sitting next to you/between your legs (*blush*)..or even HIM lying down (sitting in his chair) and you kneeling on the bed/floor next to him...it isn't about whether he could physically force you to stay there....you stay there because you want to be there and he still has manyother dominant tools at his disposal..like his voice, the way he looks at you etc. i don't really like to make any more pratical suggestions because i'm not sure what you're into, but i hope this has been of some use.
sl