Re walking the 50 miles in a day. This is easily achievable. The Lyke Wake Walk is about 50 miles and across rough terrain and most people of all ages complete this in well under a day, often overnight. I remember reading recently that Thomas Bewick the engraver of Newcastle used to go on such hikes fairly regularly.
An auld chap I recorded back in the 70s told me he used to cycle the 40 odd miles to Doncaster and back to go to work as a relieving officer.

Very interesting stuff, Joe.