Several points here since you might be new to Irish research.
Firstly, police weren't, as far as I know, allowed to serve in their home county and were transfered to other areas. The marriage certificate shows the groom's residence at the time of the marriage.
Secondly, father's name and occupation listed on marriage certificate doesn't mean that father was still alive at the time of the marriage. Also, if Isaac was a land steward he could have moved to a different area because of his job.
There's a death in civil index for an Isaac Edwards in 1885 (age 70 so born c1815) in Urlingford registration district (Tipperary or Kilkenny)- probably too young to be the Isaac you are looking for. However, if Isaac died before 1864 there will be no death certificate.