Unless you're passing other riders, ride as close as practical to the right edge of the pavement. Often, two riders can fit side-by side within a bike land, but not if the rightmost one rides on the fog line.
If you're getting tired close to the end, don't be shy about asking to draft anyone going about the speed you want to go. That might help you recover a bit. And if you feel up to it, offer to pull for a bit.
Remember to eat and drink, especially since it's June and probably kinda hot by mid day. Drink before you're thirsty, eat before you're hungry.
Take TWO tubes. I see you said you're taking CO2 AND a pump. Good thinking!
I agree with the above - take your lights, but only use them if the riders get so far apart you think it makes sense.
Got radar? Highly recommended if you're going to be passing a lot of people. It can help you adjust your closing speed with riders you're passing, so that you get there when it's safe to pass. Doesn't substitute for a look over the shoulder. In fact it augments it.
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"Don't take life so serious-it ain't nohow permanent."
"Everybody's gotta be somewhere." - Eccles