I asked the same question about the tube size, and never got an answer from the DS website, but I'm assuming (sorry I know that I shouldn't do that) that you use the same size tube as for the tire, ie a tube for a 195/70/16R you get the tube for that tire.

If you use a tube, you shouldn't have to worry about he spokes. There is a thread on how to seal the spokes if you want to go tubeless, and that's what I've been thinking about. I don't know if the tube will stay in place when rotating at high speed?

I have 8K on my tires right now, and I think I might be able to switch over by winter to the CT.

Front tire, I think MS1700 is right by getting a Metzler 880 rear tire and mount it in reverse rotation on the front. Maybe he will chime in on this. He's been running his now for a while and should have good first hand info.