No, there's nothing to prevent those hairs have come from a person or persons who who'd left West Memphis days or more before the murders, or who'd never been to West Memphis but whose hair wound up carried there by other means.
No, 0.12% is simply Fedor's estimate is the percentage of "the population could also be the source of that cigarette butt DNA", and hence doesn't rightly do anything to narrow down the percentage of the populations which could be the source of the other mtDNA samples.
Sure, but he doesn't explain why Baldwin and Echols can be excluded from the hairs which have only only two polymorphic differences from their reference sample respectively, and page 2 of this
Bode report states "in standard reporting practices three differences are required for exclusion."