With our rig wired for 50 Amp, we use a 30A/50A adapter (dogbone) at the pedestal. Just make sure you don't try to run both AC's at the same time. As for your teflon lube plate, we use the thinnest available. Don't think that the circumference matters all that much. With our PullRite hitch, we don't have a lot of play between the hitch plate and the pin box, so need to be sure that we ride up on the plate when hitching up to make sure we don't high-hitch.
If you're interested in an easier way to handle your heavy, stiff 50 Amp cord, you might consider a MorRyde cord reel. It mounts easily in the basement, doesn't take up much room at all, and makes deploying and stowing easy-peasy. One of our kids got me one for Christmas a few years back, and I thank them every time we set up someplace, especially when it's cold.