My understanding is you are required to carry canisters. You can bet there are human food accustomed bears on both sides of Bearpaw Meadow, (your first and second nights). My 2 cents is find a way to stay in the upper 9 lakes basin. I know Secor says Moraine lake is beautiful 3x, but I was underwhelmed. I camp just east above V lake at 11100' or so (not looking at map right now), in a flat patch with two streams. It's an unusually nice place.
Correct. It's an entry quota. You'll pull your permit at Lodgepole and state Whitney Portal as your exit point and "try" to make it there on that day. I did the HST last year and was all spooked about the same thing. We both entered the Whitney Zone and got out a day early, stopped and talked to the ranger at Crabtree about it and other things, and even that was no problem.
I've heard stories of poeple being turned back on the MW main trail on the way up from the E but once you're there, you're there so to speak. No sensible person is going to turn you back at Guitar Lake and have you go 55 miles when a hamburger is 10 miles to your E in civilization.