Hello Luis,
one comment about your water intake. And granted, I am no expert and only repeating what was suggested to me (and that worked)...
My first time going up the switchbacks I brought 3 liters and I drank two liters just getting to trail crest. I drank the third liter going from trail crest down to the spring on the switchbacks. (obviously I didn't summit that year).
One of the whitney veterans suggested that the issue wasn't as much thirst as it was dry mouth. He suggested sucking on a piece of hard candy (jolly rancher). I'm not sure if that is to keep your mouth salivating or to keep your mouth closed so that you aren't mouth breathing as much, thereby causing the dry mouth.
Last year I did the hard candy thing and it worked beautifully. I drank one liter going from the spring on the switchbacks to the summit and one liter on the way back.
