As a matter of interest, Gary WEMYSS is a cousin of mine and the research he refers to was mine, done nearly 20 years ago - so please blame me rather than him!
In the light of information you sent him I am quite certain that you are on the right track and "our" David WEMYSS is not yours - though I'm still not entirely certain who yours is?
Our David was a master mariner & Commander of the ship "Brigand" when he died in Calcutta in 1840.Apart from our ancestor, John W, who he left in the charge of his Indian tutor, he also mentions a daughter Maria( I think, the script is obscure ) and a brother(?) John who was Collector of Customs in Edinburgh - but significantly no wife so one must assume that she was dead by that time.
We don't know David's age at death because his burial was not recorded in Bengal so our evidence is currently a bit scrappy.
More research is needed and might be easier now that more records have been indexed and published, or otherwise available.
My research was done a long time ago and used only the records available in New Zealand at the time - no Internet of course - and your data is the first I've ever seen which will help in this branch of our family.
There are a number of points in your posting to Gary which I may be able to clarify - but I haven't had time to absorb it all!
1.Glasgow was/is a big, big, place and contained many parishes of which Gorbals & Govan are two. 2.Similarly, there's no problem with Abbotshall & Kirkcaldy as they're only a couple of miles apart & Aberdour is not far either. 3.The apparent two marriages in Lanarkshire & Kirkcaldy are no problem either.One is the actual ceremony and the other merely an advertisement ( or publication of the banns ) in the other participant's parish. Though it's always possible, and quite permissable, for there to have been two ceremonies but it's a bit unlikely.It's also possible that there is an error in one of the dates ( for the banns ). 4.I don't have much trouble with the stated ages of David & Helen in your 1850 census.I do believe that Helen was older than David by at least as year or two and it was quite common for men to be embarassed by such, so falsifying their age.Though it's also possible that neither knew their precise birth day - and we can only refer to their baptism date, which is not the same thing. 5.Do you have David's and/or Helen's age at death?