Just adding a bit...
From POR, you will want to grab the first marathon bus post start (usually around 6:30-7 am. It will drop you at the marathon finish area. Walk to the monorail station and take it to the TTC. The math is real simple, take you runner's pace and multiply if by 9 miles. take a little time off for a buffer and you should be OK. You will be stationed on course left so tell your runner to look left as they make the little tramway underpass.
Then it is a really short walk to the Poly. Again, you are on Course left.
You should be OK getting back to Epcot for the finish. AK and DHS are usually out of the questionf; unless your runner is pushing a 15 minute or so apce; and even then it may not be doable.
I would suggest that a burning of a pass and stationing yourself at Mile 25 or the point where the marathon course reenters Worls Showcase is a great spot for fans. You then have a short hop to the front gate while he makes his way the long way around the park.
One other thought; you may want to take a cab to the TTC. Traffic is unecumbered from POR to the TTC and there is a taxi stop at the TTC.