Re William and his occupation !
Most Irish Catholic Esquires of the time were actually farmers.
They would have been well respected in the area and were usually elected by the locals to Justice of The Peace.
As we were under British Rule at the time, the title of Esq was then passed on to these men.
I had a look on findmypast.ie and USUALLY most Esq feature at some point in the newspapers BUT I can't see any mention at all.
Of course it's very possible that the above theory does not apply to William.
Also, USUALLY Esq feature on the Irish Wills but I can find no trace of William there either.
Was it ever mentioned WHERE he died or WHEN he died ?
Again, Shannon Harbour is an address that I find tricky to work with.
Does the article refer to Shannon Harbour, which a small townland OR is it referring to 'A' Harbour on the River Shannon HUM

The River Shannon itself runs through a lot of counties. The article refers to Shannon Harbour, King's County (which is Offaly now, just so you know) BUT I have found records, given it's border lines in Offaly, Roscommon, Westmeath, Leitrim & Galway.
Lots of questions and theories I know But 'thinking outside the box' here MAY help get leads.
Tara