I'm looking to get a full size spare tire for my vehicross. I have the 16x7 wheels with the 38mm offset. So all isuzu 16" wheels have the same offset? Can I just go to the junkyard and get a rodeo 16 inch wheel for the spare tire and have it fit without screwing up the torque on demand if I ever do need the spare?

Can't help you on which vehicles had which offset wheels but, the 38mm dimension is backspacing, and backspacing just affects how far the tire rides away from the wheel mounting surface, or how much it appears "tucked in". The only time offset is a big deal with a spare, is if the offset doesn't allow the wheel to clear the caliper. Or if you have to run it on-road, and you have tire inside fender laws and the offset makes it stick out.

I would suggest getting the same offset if possible so then you won't have strange steering issues if you run a different offset spare in front on-road.

If the spare wheel/tire is the same diameter of the other 4, I don't see how it could affect the TOD.