Hi Roy and welcome. Don't use any one of the products you listed. You want to use a dry lube on it, one without silicone. Once freed most have had it work okay again. Try heating the adjustment ring up before spinning it. The heat will stretch it and loosen the fit. That is how everyone in the last few years managed to free it first. I know it's fairly obvious but I have to cover it and that is the lock nut loosened off? Does the base spread when you do loosen it? You can try wedging a thick screwdriver between the clamp ears and see if that helps. The motor should slide out of the base with the ring when you do this.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.