I was told by the organisers that overseas ballot entries were given priority over Japanese residents and that the chance of being successful in the ballot was about 90% (to encourage tourism and the obvious economic benefits that come with it), BUT that was before it had become a major and probably wasnt on many runners radars. I would imagine the interest from overseas runners has probably increased hugely with the prestige of being in that select group of races, and that percentage has probably reduced somewhat. I'd still say you have a reasonable chance though, so its worth a try. Its a brilliant race (I did it every year from 2010 and 2013) and Tokyo really gets behind it!
I did it last year, and doing it again this year (off at 4:10pm on Saturday afternoon). Driving is actually remarkably easy until you get close to the venue, and even then, its not congestion that causes problems, but road closures. Its not particularly well sign-posted around the area, but if you take the A13 and then the A112, it'll lead you straight in to the East car parks. Driving is definitely the easiest way though!
It involves getting to Epcot early, doing the attractions and rides in the morning/early afternoon, then hitting Canada at about 3-4pm for a pint of Moosehead, then Britain for a pint of p*ssy lager, then France for a glass of wine, and onward through the 11 countries in the World Showcase, trying a different alcoholic beverage in each one. It took us a good 5 hours last time, and I dont remember what was going on by the time we reached Mexico, except that we started with 2 people and finished with about 40! Then its fireworks and a bus back to the hotel. And a horrendous hangover!
Staying at Disney hotels is definitely the way forward on race days. We stayed at the All Star Sports last time, and will probably do the same in 2016. Its no-frills, but its clean, its comfy, its fun and the transportation to and from races is a HUGE benefit, especially for the longer races!
As Charlie4 mentions, the food in the resort cafeteria isnt really geared towards runners (its burgers, pizza and hot dogs!), but if you have a car, you're never more than 10 mins from a Walmart or a load of restaurants.
Also, if you're travelling without kids, Id recommend the "Around the world drinking challenge" at Epcot in the Monday night. Its unofficial, and Disney dont really recommend it, but it was a lot of fun. Lots of medal-clad runners on bar crawl around the World Showcase. We made a lot of friends that day/night!