Don't know if it'll help much, but I try not to look up when I'm climbing a hill. It's less demoralizing seeing the next 50 feet, as opposed to looking up and seeing the hill going on for hundreds or thousands of feet. I figure I'll know when I hit the top once it gets easier to pedal. The other thing I do once I reach the top is to continue the same effort for another 10 or 20 seconds going down, even if I'm pooped. The rationale here is to get to the balancing speed on the downslope as quickly as I can, then mostly let gravity take over. Simply put, there's more bang for the buck in terms of effort versus percentage speed increase putting in a good effort when you're still going 15 or 20, rather than 45 (hope that made sense). All that said, the hills I encounter aren't in the same league as what you're dealing with. A normal 1.5 hour ride for me usually involves 500 or 600 feet of elevation change.
Can't really comment on the calorie intake part. I've done rides over 3 hours without eating or drinking. I do drink quite a bit right before going for longer rides in warmer weather.
BTW, that looks like a nice route. Nothing really like that where I live.