Coolshinney is a townland in Magherafelt parish. Griffiths Valuation for 1859 list an Alexander Wylie farming there. He had plot 2 which was a 15 acre farm.
There’s a death for Robert Wylie aged 74 on 1.9.1879. He was a cottier (small farmer) and a widower. That fits with the age and year of death you have given.
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1879/06510/4874888.pdfA Robert Wylie in Coolshinney in the 1831 census. Family were Presbyterian:
http://www.census.nationalarchives.ie/pages/1831/Londonderry/Loughinshollon/Magherafelt/Coolshiney/18/Alexander next door (so possibly related):
http://www.census.nationalarchives.ie/pages/1831/Londonderry/Loughinsholin/Magherafelt/Coolshiney/21/Another Alexander also nearby:
http://www.census.nationalarchives.ie/pages/1831/Londonderry/Loughinsholin/Magherafelt/Coolshiney/17/And a George:
http://www.census.nationalarchives.ie/pages/1831/Londonderry/Loughinsholin/Magherafelt/Coolshiney/20/1 Wylie family there in 1901:
http://www.census.nationalarchives.ie/pages/1901/Londonderry/Ballymoghan/Coolshinney/1532020/All those fmailies were Presbyterian. Magherafelt Presbyterian baptism and marriage records are copied in PRONI’s records as follows:
1st Magherafelt Baptisms, 1771-81(with index), and 1813-1964;
marriages, 1769-82 (with index), 1819-28 and 1845- 1963; marriage notice books for Magherafelt Presbytery, 1845-1946; session minutes, 1703-82 and 1818-56; committee minutes, 1848, 1852-3 and1911- 45; list of elders in 1828; ministers’ visitation books, 1823-32 and 1841; ministers’ diaries, 1833-54; ministers’ account book, 1889-1904; history of the congregation prepared in 1853.
You may find the visitation books very helpful. The Minister went around every family in the parish, townland by townland, and noted who was living there (plus some who were absent, eg emigrated to America). These records are not on-line and a personal visit to PRONI is required to view them.