Take it out again, you won't be able to figure out what's failing unless you get it to fail, once it has failed check the coil for heat and see if there is spark. My money is on the coil.
That sucks about the leafs
Rear shocks are not the same as xj but you can find ones that fit, doesn't have to be Comanche
Taillamps woulb be either ebay or classifieds, key motor parts is coming out with some soon but no eta