Building MTB Single Speed

thats a lot of work - rebuilding your wheels for the sake of saving a pair of hubs.
if you want to keep discs then I would use the wheels you have got.
I suggest giving it a try using what you have + spacer kit + tensioner + chainring.. 44-16ish
If you want a road frame then you won't need disc brakes.
If you want a 29er then you are better off buying one complete second hand they have a high turnover.
You will end up getting another bike anyway, surely.. ha!

Yes, I will keep the frame, go to single speed (not fixed) - but what about the wheels?

Is there any way I can get rid of my bulky tyres and get some sort of road tyre on my existing hubs?