Where does my bathtub vent go ??? Pic included

I'm not sure your distances, but you should be able to combine your tub drain with the shower drain. If you're using 2" drain, I think the distance is 8' from the trap to the vent. http://publicecodes.citation.com/icod/ipc/2009/icod_ipc_2009_9_sec006.htm

The south wall would be fine to run the vent.

I'm not sure what you mean how high up does it have to go to form one. The vent can not run horizontal until it is 6"s over the flood level (the highest point the water can fill) of the fixture. It has to extend i think about a foot over the roof, and there are also limits to how close to a window or other openings it can be.

Oh sorry, I meant combing the drain and the vent for both. At least the inspector here allowed me to (and I wouldn't see why you couldn't) have one 2" drain for the shower and tub. I would run 2" drains having the tub run into the shower and then one 2" vent running up instead of having 2.

Just checking...I hope "vents up to the attic" does not mean terminates in the attic.

They may require that where you are, but it seems according to the 2009 code, you can have a single vent.
http://publicecodes.citation.com/icod/ipc/2009/icod_ipc_2009_9_sec008.htm

Just checking. I had two vents all ending in my attic when I bought my house, and then the two exhaust fans on top of that.