at what point do you cut all this stuff out pre-contest:
artificial Sweetners, diet sodas (including soduim-free), crystal light, SF gum.

Diet Soda & Crystal Light Wed.
SF Gum -- don't worry about unless you are chewing enormous amounts. Splenda has no sodium and 1/2 g carb per packet -- I used some with my oatmeal on Wednesday night and after that I was eating grapefruit and hamburger until after the show.