There have been quite a lot of local histories written about life in old Orkney. You might want to make an enquiry to www.orcadian.co.uk - this is our local newspaper, that also publishes local books and has an online bookshop. If you wanted advice on what books might be most useful, I'm sure you could email them with your requests.
We've got your William T. Seatter. c. 26 August 1826 in Evie and Rendall m. Jane Helen CHALMERS d. 11 January 1890 of Cirrhosis of the Kidney at Rousay Father: William Seatter (Farmer) Mother: Lydia Ann FLETT
Your William T. Seatter is a brother of my 3x great grandfather James Seatter.
You probably have this but here goes! monumental inscription at corse, wasbister, rousay: ( granite stone built into wall) sacred to the memory of william traill seatter farmer saviskaill born august 22nd 1827 died 11 jan 1890
Did you get his parents names from his death cert? if they are William and Lydia they are on the census info for Walkerhouse, Evie quite a big farm and had a large family