Hi Cheryl, I can answer some of those questions for you, I volunteered at last year's events.
The half marathon and marathon both start in the same place in the Epcot parking lot. There are fireworks and a great opening ceremony and such.
During the half and the whole marathon, there are stations at every mile marker. I worked at mile marker 16, which was a water/powerade station. I know there are stations with powergel and other things, I just don't know where they are.
After the start of the event, the half-marathon and the marathon participants seperate for the 3.3 miles before merging in the Magic Kingdom.
The half-marathon's finish is on Floridian Way, past the Polynesian, heading towards Animal Kingdom..
Water Stops/Sports Drink Stops are at miles 2,4,6,8,9,11,13-25 as well as both finish lines
Fruit is at miles 13.2 and 19
Powergel is at 16 and 19
Sponges at mile 17.3
Candy at mile 23
Dole fruitbowls, breakfast bars, and muffins at the Half and Full Finish lines
Hope this helps, any more questions, I'll be glad to answer.