A higher score indicates more severe fatigue impact. I'm gonna guess it's about at least 25% reduction in fatigue for the participants, given a fatigue score of 120/142 (very, very high). However, the drop out may have been a negative score.
I tend to not overthink the autonomic stuff. It's messed up, and it's a little different in everbody. Most seem to have problems with things that increase vasodilation (heat, standing, alcohol, stress, as you mentioned). Some benefit from mild vasodilation, and maybe this study only had those people. But there are a lot of drugs that vasodilate/vasocontrict many have tried and not many would say they truly treated their fatigue by 25%. Even in a small group of 6 that would be rare.
If it's published next year, it will be interesting if the author noted improvements or worsening of autonomic function irrespective of fatigue.