hello jacob, as esavage is ofline, here is a link to thread locker
http://www.loctiteproducts.com/threadlockers.shtml. you can get similar thing in a tool shop
you can also replace the nut with a fresh one, the nylon af the end(nylock) can be worn and not effective.
those wheels are bad for you, 14mm hex, no offset, and very heavy. its good to compare the weights to the ones you already have. you can get some decent wheels that are 200-250g each corner, with 17mm hexes (add hpi86925 kit).
"40 series wheels" are also heavy. there's good/popular suggestions in the rim/tire category
gear down a tooth = gear more.. meant to mean go down a tooth on the pinion side. smaller pinion = more speed and less acceleration, there's a chart in one of the sections that show it, also the esav manual has it..
the pinion you are using may be 20 tooth, and if you use heavier wheels, you can use a 19 tooth pinion so the mating of pinion and spur is the 66t/19t instead of 66t/20t
you could also get some flat nuts that are less thick that the stock one, and use two, adjust the slipper ad you like with the first nut, then after that, put the second nut on and tighten it onto the first nut (tighten them against eachother)