I do think that you've not thought through the implications of trying to marry Humpries pulp SF with the changes in the fine structure constant.
Humphries idea is a piece of apologetics designed to explain why the rest of the universe looks so much older than the bible says it is, and to do this he postulates that time ran lots slower for us because we were inside a 'white hole' (a term he never formally defines in any consistent sense).
The evidence for the change in the fine structure constant, alpha, comes from light from very old stars, which during it's transit of interstellar dust clouds has aquired absorbtion spectra that are seemingly incompatible with the current value of alpha.
This change in alpha is on the order of 1 part in one million, and will have a corresponding effect on radioactive decay rates.
Humphries model implies that the amount of time that has passed on earth is far smaller than that which has passed in the rest of the universe, by several orders of magnitude. Thus the effect of any change in alpha will be further reduced if you use Humphries model, and the task of explaining why all these inconvenient short half-lifed isotopes aren't here is made no easier.
(As a side note, if anyone knows how Humphries model explains how the earth had long enough to form inside this 'white hole' could they post an explaination - I couldn't work it out.)