You certainly are in a jam!....there are so many issues at work here. I've noted from my patients on disability, that there are often deep psychological reasons for their disability, moreso than their actual physical problems. It could be your wife has known for years or has been troubled for years by your lack of a "whole" loving marriage. This trouble may be reflected in her physical disability.
As far as C and Z go, who wouldn't want to have two dynamite lovers in their life? All of us have had a little of the "grass is always greener" thing. Sometimes it looks so very green......
Do you thnk your wife, who you love, would go for the poly life with these two other women?