Finding out further details from the time period will be difficult, unsure how long you have been working on your tree but it took me many years to build up a comprehensive story to add to the bear facts such as marriages, births etc. It depends how much time you are prepared to give it and how passionate you are in chasing up every small lead.
John Healy was a farmer, have you looked for Estate records in the area where he was farming in the 1800's? other records such as Petty Session records also exist for the second half of the 19C
A look at the Griffith revision books would give you a rough idea when John died if the land was kept in the family. I see from the Griffith map that the land farmed by John Healy is now part of a tree plantation, the house on the plot of land seems to be gone by the early 20th century as can be seen on the OSI maps.
http://www.osi.ie/Home.aspxRecords abroad may eventually reveal further siblings on the Healy line, as at least some are sure to have emigrated. Ordnance survey memoirs for the parish of Ray from the 1830's would also help to flesh out the family story, the Laggan area has a rich history of documents stretching back to the Plantation so there are probably still quite a few avenues you could explore.
One other course is to look at ALL people in the general area sharing the surname/s you are interested in as many of these families are interlinked.