20 bucks at home depot and get yourself a propane touch and heat it up till its nice and hot.
Then use a BFH aka big ****ing hammer on the stem with the nut up side down
For what it's worth, I had the same problem on all four of the cam/caster adjustments on my LCAs and ended up having to cut them out. Which I don't recommend doing. Ever. Take it to a shop to have them handle it.
After a full day of PB blaster, hammering, heating with a torch, hammering some more, and cursing, I nearly resorted to animal sacrifice in an attempt to knock them loose. Needless to say, my sawsall was super, super pissed by the end of the project, though +1 to Ryobi for durability.
Whatever you do, get a greaseable kit. If the shop/dealership won't put a set in, buy some from Rockauto and slip them in yourself. I live in CO, so rust is about zero concern for me (the previous owner lived in OH for a time and then moved to CA), but the incremental difference in cost is worth it if I never have to go through that misery again.
As for driving without the bolt, if you have a metal file and a sawsall (or a dremel and a boatload of patience and cutting wheels), you can cut the end of the bolt off and file the burrs so you can get the nut back on. Disaster scenario would be rear of the LCA breaking loose on the way there. The bolt will hold it, but without a nut, it could slip loose and fall out. Putting the nut on, even at the very end of the bolt, will keep that from happening.
It's obviously not optimal, but if you're gentle with it and limp all the way to the shop, you shouldn't have any issues. If you haven't had your lower ball joint replaced, expect the techs to mention replacing the whole lower end kit. Once the new cam/caster kit is in, though, you can probably handle that stuff yourself.
