Yesterday, I sent another Query to John Grenham whom I originally contacted through http://www.apgi.ie/
He responded and said:
"I have now had a good look at the information you have and I'm afraid I don't think there is much chance of adding more detail to the 18th century information. The biggest problem is that Ballysadare Church of Ireland registers were destroyed in 1922. There are some surviving 19th century property records that might shed some light on the family, and there are good 18th century manuscript estate records that might add more circumstantial detail.
Were the family propertied? If so, there might be some chance of uncovering registered marriage articles or property transactions.
But I wouldn't be optimistic about answering the specific questions you pose."
So, hopefully, descendant members of the family who stayed in Ireland, when our ancestors left circa 1850 will find this thread and be able to help us fill in the blanks. I started this thread in the hope that these connections can be made.