100 ounces of water is about right for the section from Trail Camp to the summit and back. Carrying 3 liters is not necessary for the section from the trail head to Trail Camp. There are a number of good places to take water from along this route. At high altitudes, you should be sipping water quite frequently to avoid dehydration but you do not need to carry that much. Just stop and filter along the way.
There are some steep drop offs on the upper part of the switchbacks, but the trail is wide, so just stay close to the wall side of the trail.
The section from Trail Crest to the summit has some exposure, but nothing that would qualify as narrow and precarious. Just keep looking forward and walk straight through and you will be fine. I believe the entire main trail is on you tube. Check out some videos if you are concerned about it.
