1. The exit should be Happy Isles. ...Found the PDF form you were using. http://www.nps.gov/yose/planyourvisit/upload/wildpermitform.pdf
They use their trailhead entry list for the exits, which is a bad fit.
2. I think with so many people focused on the JMT and exiting via Donohue Pass, the other trails should be a lot easier to reserve. That is part of the reason they implemented the exit quota. I am not sure what their rules for camping at LYV if coming in from your direction. The LYV quota is especially for people starting up the JMT from HI.
4. If I were doing one night, I'd start at Tenaya, because that is a shorter hike. If you go to Cathedral Lakes, a night there would be nice. Take the side trip down to the lower lake -- that is one of the most beautiful spots in Yosemite. Then spend the second night maybe at Sunrise Lakes.
5. Check the bus schedules.