here's a couple more pointers for you:
Since you mentioned arm pump, try to find a few points in each lap where you can take one hand at a time off the bars and just open and close your fist a few times. Arm pump is often the result of not enough blood flow to the fore arm. So open and closing the hand will keep blood flowing.
Also, my biggest challenge in races is blisters. Even though I ride a lot, I still get blisters when I race. I found during my last HS that a tighter glove is better than a looser one for preventing blisters. So I went from an XL size to a Large. Also, since it sounds like you'll be racing through water, try to keep your hands dry. When mine get wet I blister faster, so thats when the extra set of gloves comes in really handy. Have a set ready at your gas stop.
Have fun and I'm looking forward to the report.