If you're getting exhaust in the cab, you may have a manifold leak that needs addressed. The only other thing I can suggest, beyond getting the vents to work, is to consider adding a sliding rear window. I have one installed in mine, makes a huge difference. I can open the vents, open the slider, and get plenty of fresh air without rolling the windows down or getting a bad draft through the cab.
On the suspension, if the springs are worn, the only real fix is going to either be new springs, or you might be able to have them re-arched if you have a good spring shop nearby. I don't know of anyone currently making overload shocks or a TF specific airbag setup, but you might be able to adapt an airbag system for a later 1/2 ton to work.
