Of course I can give you dates---how forgetful of me!
John Downie (b. 1835) and Bridget McCurdy (b. 1836, of the Rathlin Island McCurdys) married in Cushendun, County Antrim, in 1855.
We don't have anything else on John's parents, Robert Downie and Margaret McGeachan, except that Robert was a soldier. We're assuming that they're about 20 years older, which would mean birthdates circa 1810?
Even if this doesn't lead to anything, thanks for following up! I do appreciate it.