Well, Zbrush is pretty much unusable without a keyboard, and sculpting programs in general don't benefit from a tablet display anyways. Therefore a cheapo laptop + a small or medium wacom tablet setup seems like a rather obvious and straightforward solution.
No I'm not sure. If it's messing up then I probably wouldn't use it on a Wacom monitor. Personally I haven't run it on a cintiq. Just desktop monitors.