First of all, its not clear that Mary Magdalene is the subject of John 8. Thats merely tradition.
Second, there is nothing in the context of John 8 that suggests its OK to continue on the with the adulterous affair, going so far as to divorce your spouse to marry the one you have been fornicating with. I wonder if adulterer and adulteress were attending Mass together.
I trust that Newt and his third bride have found true repentance and conversion to faith in Jesus Christ.