Olive oil separates into liquid and semi-solid components when chilled. That's probably why you want that to be at room temp. Also, maybe if it were cold as it entered your stomach it might trigger the flow of bile less suddenly and forcefully, which would be less effective. Just speculation on my part.
I don't have much to say on the water topic, other than to repeat my opinion that Epsom Salt doses #3 and #4 serve only to dehydrate you and can (and should) be omitted. I'm open to hearing a reason why those two morning ES doses are called for, but on my own I can't imagine what good they might do.