The defrost is the default position without vacuum. As indicated, you have an issue with the vacuum lines. Do a search and there are posts with diagrams.
The fan spped is seperate. What year do you have? 97-02 it is not uncommon for the switch to have issues. Dos it work if you jiggle it? If not it is most likely the blower resistor. When my resistor went, the fan speeds went one by one.
2003 TJ, 33" BFG AT, 2" BL, 2" BDS spring lift, Truck Lite headlights, Homemade sunrider top.