I think this is more to do with the accumulated mental and physical strain of the challenge and it could drag him below the required rate quite quickly. I think he needs to get to Florida soon to try and break up the current mindset.
I think you are right.
I read the posts on FB and just wanted to say - FFS you've gone through SO much this year with illness, accidents, mechanicals etc and you can't cope with getting some wet weather gear and getting on with it when it rains? BUT then I realised, it may just be that he is getting close to the edge and in fact, is struggling with the overall accumulation so didn't want to sound cruel!
Hope he shakes it off, and he gets back down to business and deals with it.
Show's how incredibly tenacious TG is though, even with acclimatisation, the UK weather is tough and unpredictable compared to what Kurt is struggling to deal with at the moment. Whatever the American record attempt ends up as, I must admit, I will always feel that it isn't comparable to doing it in the UK with our ridiculous roads, junctions, traffic, variable climate and drunk-moped-riders.