This isn't much help, but I think the death of a wife might be more likely than a failed marriage. Have you searched for record of the death of Margaret or Isobel? And perhaps James Wilcox might be found in death records.
I have several cases like this among ancestors, men with several wives in fairly rapid succession. Sometimes there is a reference to the death of the earlier wife. I have two wives who died in childbrith and the husbands remarried very soon, probably because of the children. All sorts of interesting things as you look around.
It looks like you are doing a lot of investigating, keep it up.