Hi Chef, welcome to Neurotalk..
I had that same problem bad with my right foot before I had my lumbar sympathetic nerve blocks, since then my wet heat tollerance is somewhat better.
I also melted my epsome salts with hot water, then cooled the water
before taking a bath to avoid hot baths.. the epsome salt soaks do help the pain and inflammation.
As for bearing the pain I am not sure what would help
you before a shower, this is what helpes me.. I used to load up on the ibuprophen before bath or shower because it wouldn't woose me out or effect my ballance, but I have to cut down on those now too. Showers can get so they seem to be throwing pebbles at ya too, even on low pressure so if my pain levels were already high I would take a stronger pill or smoke one of my herbal pain relievers first, usualy helped.
I tend to have neutral bathes and my right origional RSD foot tends to wander out of the water alot.. epsome salt soaks actualy.. great topic thanks Chefsuzz and again welcome, post away any questions you can think of this is the place.. Wonderful people here.

Sandra