"I think it was John Muir who said he had never been as cold as in summer in San Francisco (fog season- steady 50-60 degree weather)."

Not John Muir. It is often attributed to Mark Twain, but apparently he never said it either.
There are lots of sites that talk about Twain's quotes - this one is probably as reliable as any-
http://www.snopes.com/quotes/twain.asp

As for the sleeping bag problem. Anyone in a Snow Leopard in 50-60F weather should be far too warm to get a good night's sleep. It is rated 0F. My old Cat's Meow, originally rated to 20F is too warm for those temperatures and it's long past its prime. There must be another cause. If you are sleeping on the air mattress, it could be sucking the warmth out of you, but I suspect some medical issue. I get cold very easily (hence the huge parka in my photo) and sleep fine around 10-15F in a bag rated 23F, plus either an overbag and bivy sack or my parka on top, while wearing my Capilene midweight base layer I mentioned above.