1. I think 7 hours sound right. 14 miles. 2. I think even with a little traffic you will be 1:45 3. There are water sources but I don't have the specific info I've seen on sources at my fingertips. There is a nice lake I have a picture of below:
If you have a little extra time (even an hour or so) a slight side hike into Tenaya Canyon is amazing. It is fun to find the sign that states: "Warning: This is not a trail. Travel beyond this point is dangerous without climbing equipment. Return to Tioga Road."
It is safe to go past this sign a bit and see the amazing bowl of granite. You can easily and safely hike as far as you want into the bowl but at least go far enough to see the Half Dome vista open up. Here is a good site explaining this side trip. You start at the Clouds Rest trail and instead of going up you follow the creek which will be dry now.
