1.) It's not in Camera, it's in World (setClippingPlanes()). For the software renderer, only the far clipping plane is really relevant.
2.) I've no idea. Just try some things, but be sure to call setFOVLimits() once with proper boundaries or your changes to very small values will be ignored. Don't ask why this method exists...i can't remember that. Precision is 32bit but because it's actually a w-buffer, precision will decrease in the distance.
3.) That's easy: You can't! You can set an additional color per object but not per vertex.