Corned Beef Question: Should I remove the 1/8 inch of fat on one side of my brisket before putting it in the curing mix?

No . . . the fat adds flavour. If you cook it properly, the fat will melt away. If you did a chemical analysis of a brisket with all the fat removed and one without, cooked them the same and then removed the fat from the original untrimed one, there would be little to no diffence in the fat content, but the fat brisket would have more flavour.

I don't. I just started mine a few minutes ago.