Delta shower valve repair
I am attempting to fix my leaking Delta shower valve. It is a single control type, see the attached picture. I started yesterday trying to disassemble it to replace the springs, seals, ball etc. I know that if I try to force it off that I will break three copper pipes behind the valve. I have been attempting to help my cause by applying my home grown liquid wrench (ATF and acetone 50/50) to the threads, and heating it a bit with a hair dryer and a plumbing torch. So far, 1 day in no luck. I am considering attempting to dremmel off the dome piece and/or the cylindrical piece that covers the pipes, but thought I would look for recommendations here first. I would prefer to not replace the valve, but I do have access behind the shower in the wall of a closet if necessary. One thing that prevents me from just diving in and cutting the metal is the availability of replacement parts for those pieces. I have not looked terribly hard, but have not found them yet. I failed to ask about them yesterday when I bought replacement parts for the internals at the plumbing store, but I did ask about the plate behind the valve and they did not have that.