I am an avid Cain(e) researcher but only have minimal info on your line.
I do have the will of Barnabas' grandfather William who died Dec 10th 1777, his will is summarized in Manx Note Book.
I happen to have the full will which apparently is among the many that fell off the index when the various switches were made. I'll see to it that the will is sent to those who are working on the index.

I have no info after Barnabas and Elizabeth except the 1836 will for B you may have seen--it, too, has fallen off the index.

If you have your data on genealogy software I would be pleased to receive your line in gedcom format--I can send my info to you.
My email is djdorca @sign comcast.net--fill in spaces and take out "sign".

Donna