I run around the EPCOT resorts when I'm there, and I can give you accurate numbers (yes, I'm a gadget geek with a GPS).
If you start on the path just behind Jellyrolls (at the foot of the bridge), and walk to the MGM Studios ticket area, the distance is 0.75 miles. The distance is about the same from the Boardwalk lobby, if you go out the front, veer right, go between BWV and the tennis courts, and get on the path there.
From the Boardwalk lobby to EPCOT's International Gateway, the walk is less than 0.5 miles. I've not run or clocked this, but it's 0.8 miles around Cresent Lake, so the International Gateway must be much less.
