Kitsap, The low volts on your gauge would indicate me that your alternator is beginning to fail, easpecially since you are seeing it when driving down the road with the engine and multiple accessories running.
The fact that you can't pull your sparkplug wire boots off the plugs really disturbs me. If you have corrosion that bad at the plugs then you probably have it at the other end of the wires as well...I.E. where the plug wires connect to the dist cap and most likely corrosion on the coil contacts and coil wire or even inside the dist., as well. Corrosion at any of these points I've mentioned can put a tremendous extra load on you electrical system and cause the problems you are having.
Brian "Buck" Buchanan, U.S. Navy Chief Petty Officer (RETIRED) - 87 XJ Laredo, Ol' Red - 8.5" Rusty's Offroad/Rough Country lift, D30 trussed and D44 high clearance shock mounts, 4.56's, Aussies, Chromos and Disc Brakes front and rear, JCR Offroad Belly Skid Plate and Stage 2 Rock Sliders, Off Road Fab Winch Bumper and Quarter panel Guards, Liberal Front Wheel Well trimming and Rear Wheel Well Cut N Fold, 35" Goodyear MTR with Kevlars, Cobra CB and AW4 First Gear Lock Crawl switch, SYE, Stock XJ driveshafts front and rear and Milemarker SEC8000 Winch.
91 XJ Sport (Old Gray Jeep) - Layed to Rest (04-01-13)
87 XJ Laredo (Ole Red) - (My Jeep)
87 XJ Base (The Boys Jeep)
96 XJ Country (The Daughters Jeep)
08 Dodge Charger R/T (The Wifes Ride)
04 Silverado 2500HD Duramax/Allison (tow rig)