Sounds like maybe your throttle linkage possibly isn't positioned correctly. The big screw on the mixer that looks like it's made to be adjusted with a nickel is your idle mixture. Doesn't really effect your idle speed too much, at least not dramatically like your talking about.
I would start by inspecting the throttle linkage from the floor board back. Do you know if it's a Continental flat head or a Wackashaw? get me the truck's serial # - it either starts with 355 or 235. I forgot to mention- that the "oil" you saw in the regulator is typical- that's a by-product of "cracking"- when the fuel changes from a liquid to a vapor. Some requlators even have a drain valve to drain that gook out of there. stinks, doesn't it!
Try unhooking the linkage from the carburator (mixer) to eliminate linkage problems. Is there a return spring for the accelerator linkage?