Hi, yes nice simple answers:
1 everything matters, musuloskeletal durability about one of many things... weather, lungs, breathing, mental strength, topography, heart, kidneys, knees, stomach, nose, throat etc etc. You name it, it matters.
2 in a nutshell, far more is available on west coast than east which is pretty much always nyc. Yes, Florida slashes by loads, of course it does. I think distance must be 2850 at least. Technically a Transcon is ocean to ocean and I simply can't understand why folks don't go the extra 5 miles in NYC. It seems so obvious the crash into the waves on the other side.
3 As you write, a huge revamp in his schedule... let's see if that helps.
4 there are at least 10 different ways to fudge/cheat and the UK editor of Runners World has just been busted for a couple. Admits it was down to her ego, and she does a lot of runfluencing. Strava is very easy to upload from excel, so you can basically say any old thing. The likes of WG and RB are bright enough to have carried this ruse for as long as they did, but now are surrounded by questions and controversy and can never try anything like this again. Many have said his cadence is odd but he could be watch muling or just putting in cadence from any old run. The HR looks just about believable to the naked eye, which is how they got away with it for so long, and some people say it is possible to run at 105 in this. It's absolutely not. But their number one defence is that "HR data is bullsh*t". But it's absolutely fine, works 99% of the time [as this challenge is clearly showing, and it works for WG and RB in all their other running, when they're not doing publicity multiday fundraisers].
So what with some saying the HR is possible and others that the HR is just Garmin and Coros being hopeless, I have had my hands full.