you will gain no additional info at the Records Office (by which I assume you mean General Registry) - their only info for this period (some 80 year or so) prior to civil registration are the transcribed parish registers dating from c. 1911 copies of which are on Mormon film and provide the extracted records in the IGI.
The marriage of Wm Couter/coulthard to Alice Fargher is probably lost in the missing Marown marriage register - the Bishop's transcripts fill in most but not all of the gaps from 1733 (see Manxnotebook for my transcription + comments) - there are significant gaps in 1792 + 1793 which would be approx when I'd expect a marriage with first child bapt in 1795
Alice Fargher is assuming census ages + death are correct born c.1770 - the only candidate I can see is d/o Philip fargher in Patrick in 1772 - no mothers name is given in the reg (at least not in the 1911 copy) - there are only two children to Philip in this time period 1768 + 1772 - I cannot match him with any wife except possibly Ann Dawson as the marriage states philip kk marown, ann dawson of peel married kk patrick; - I suspect Ann's will is in 1807 but not one I have looked at - I havn't found a will for philip but his burial might be that in 1824 in Marown.

The original parish regs have been digitised and are supposed to be made available once the new iCentre opens (some time this year but when ?)