Welcome to the forum, YS!
1. Plan on using rocks at Trail Camp. The tent sites are mostly on pretty thin soil.
2. It CAN be windy at Trail Camp. But it just depends on the weather. Be sure to click on the Weather link above on the left, and select several of the weather links on that page to see what the predictions are just before your hike.
3. I think most people average 2 hours on the switchbacks, and another 2 from Trail Crest to the summit. Carry 3 liters of water (last water is at switchback 20 above Trail Camp) Drink one on the switchbacks, the second on the way to the summit. You could stash the empty bottle and the third liter at Trail Crest for the trip back.
4. That is what most people do. Only some leave their tents up ...and unzipped so the varmints don't chew a hole to check inside.
Now, a suggestion: Be SURE to acclimate by staying two nights at altitude before you head up to Trail Camp at 12,500 elev. Lots of people experience altitude issues by backpacking to that height. Staying at Whitney Portal (8k) is good, and up at Horseshoe Meadows (10k) is better. If you can't acclimate that long, consider backpacking only to Outpost Camp at 9,500 ft, and make a longer day hiking to the summit and back. You could even spend a second night at Outpost AFTER your summit day.
For more reading, click on the Orientation Notes above on the left.
