No 2BR availability for BW as of yesterday, only 1BR. Taxis will be available until the end of the party so it should be easy to get back. One thing to keep in mind, if you are grabbing a taxi, it will likely be shorter to walk to BC and grab a taxi from there if you are back in the world showcase area. Otherwise you will have to walk out to the bus stops in front of Epcot.
I don't think that there will be a huge difference between the other DVC resorts. I believe OKW would be the closest followed by SSR, AKV with VWL and BLT being the furthest away. I don't think it will make much difference in time or taxi fair the evening of the race. If you don't get BWV or BCV, then I wouldn't make your choice on proximity to the Epcot due to the race. Instead pick which resort you will enjoy and will work with the remainder of your trip. Disney wants non resort guests to make there way to Epcot and they provide shuttles to the race start from there.
So if I understand correctly, we can get transportation to Epcot and then pickup a bus to the start from there?
Thank you so much for the information.