Nice find,
Puddleglum! There are also several world maps reproduced in that section (one of them, with the shapes of the continents starting to look similar to what they are now, can be seen
here). Judging from those, I'd say Belegaer pre-Fall looks like it's roughly the size of the Atlantic - which is something between 3000 and 6000 km wide, and it took Christopher Columbus a little over three months to cross it; which fits your guess of about 12-14 weeks quite nicely.