Maybe I'll see you on the trail. I'm going north to south, starting July 14. Which direction are you going?
I would ditch the gaiters. Not enough snow or bushwhacking on this trip to make them worth the weight. -7 oz
The heavy hiking boots are a matter of taste and style. They will be much less necessary if you can cut your pack weight.
Replace the heavy rope with lightweight cord. The stuff I use is from owareusa.com (click on Flat Tarp, scroll to the bottom of the page, 1 mm cord, $10). -2 oz
Ditch the water reservoir in favor of lightweight half-liter bottles, like the ones they sell supermarket bottled water in. -8 oz
I guess part of the reason your pack weight seems so extremely high is that you're figuring in 3 liters of water. I should check this myself, but I don't believe streams are ever that far apart on the JMT. One liter should do it. -35 oz
Replace the thermarest with a 4-oz, $16 closed cell torso pad http://gossamergear.com/cgi-bin/gossamergear/nightlight_torso.html -34 oz
Lose the trowel and use a handy rock for digging catholes. -3 oz
Replace the heavy first-aid kit with something more lightweight. This might be as simple as dumping anything that's not useful and repackaging the rest in ziplock bags. -5 oz?
Dump the towel and use the spare shirt instead. -2 oz
Replace the filter with iodine or ClO2 tablets. -5 oz
Chop out the necessary sections of the guidebook and leave the rest at home. E.g., Wenk has both S->N and N->S, and you don't need both. (Actually I just decided to copy the relevant info from Wenk onto the back of the Harrison maps and leave the book itself at home.) -8 oz
2 lb of food per day is a lot. Of course it depends on how big you are, how many miles you do per day, and how energy-efficient your food is. I weigh 140 lb, and I find that 1.4 lb/day of food is about what I need. You might want to post more about what kind of food you're bringing. But assuming you can make it 1.4 lb/day... -96 oz
You're assuming 10 days without resupply, which is presumably Muir Trail Ranch to Whitney Portal (assuming you're going N->S). I imagine that you've gauged how many miles a day you could do on your most recent hike, found it was about 12 miles, and came up with 10 days. But if you were doing 12 miles with a 48-lb pack, you should find that you can do a heck of a lot more miles with a more reasonable pack weight. I suspect that with a lighter pack, and once you're in the groove, you should find yourself doing more like 15-20 miles a day. This would cut your days without resupply down to more like 7. That cuts your food by an additional 4.2 lb.
Keep in mind also that you have various opportunities to feast on food that you don't need to carry: Double cheeseburger and fries at Tuolumne, ice cream at Reds Meadows, luxury food that you pick up at your resupply points and eat immediately.
Total weight saved: about 17.0 lb, which reduces your pack weight from 47.9 lb to 30.9 lb.
Have a great trip!