I also recommend North Gate to Summit #1 then descend the south side to the Athenian School and come back up South Gate to Summit #2. Might as well get the hard one out of the way when your legs are fresh.

Ditto on the suggestion to use easier gears and not worry about your times.
Food? Ask 4 cyclists you will get 5 answers on that one.
Me? I like some protein and fat after about 3 hours of continuous effort. PB&J, Perpreteum, Balance Bars, all good sources and don't forget the power of a Payday candy bar. Some of the science suggests that you perform better if protein and fat are added to the mix during long efforts.
I find it to be true for me.

Good Luck with Los Dos Diablos