Hi purplekat,
I wouldn't be able to give up. I've tried several times in the past, and it's the know that the next certificate might turn up something new. It's only because I came back after "giving up" several times in the past that I found Alexander in 1861, In Roxburghshire. Not nearly what I wanted, but it was still that little further back than anyone knew before.
And given that Alexander's father died after the SSRs were introduced, it's probable that somewhere there is a death record of John DAVIDSON, farmer, widower of Margaret WILKIE. I know it's not definite, but I'm still looking.
Like others on that thread, my eyes have been opened by the number of people miraculously born so soon after a wedding. It does end the suggestion that Alexander's father was illegitimate and so therefore his marriage and his son's birth are not in the church records (something I never believed even a little bit).
Frustratingly, I also have problems with my paternal great great grandfather, who was born in the Falkland Islands. My father has struggled for years to find information on him. These things were sent to try us! Good luck with your own research too.
Tim