Help! How to find family connections when no documents

[medhist]

Hello
I have managed to trace my McAllister roots from the early 1800s but because I can find no burials, MIs, wills, many baptisms and even marriages it I am at a complete brick wall to get back any further.
I know that Alexander McAllister was born c1799 at St Ninians, Stirling from censuses. His parents from his death certificate were John McAllister and Isabella Ferguson. The family lived in Dalmuir, Old Kilpatrick, Dumbartonshire and links with Rutherglen, Lanarkshire. John was alive in Dalmuir in 1841 census but no sign of him afterwards. Their marriage is recorded at Kilmaronock, Dumbartonshire in 1798 but no trace of the baptism  of them or their children.

 At the marriage of my great grandparents Alexander's daughter Margaret married her cousin George, son of John McAlister. All lived in Dalmuir or Rutherglen. After 1860 they moved to Glasgow. Since George's father John McAllister b1804 in Denny, Stirling, died in England. I don't know whether he had the same parents as Alexander. John may have been a half brother to Alexander or the son of another son of John and Isabella.
Can anyone suggest how I can crack this problem please?  Is it likely that marriages and baptism would be recorded in FRee church records (nothing in Catholic records)? I live in Swansea so a trip to Edinburgh to try to find them in free church records would be a major expence so I would need to know if a visit to sturdy free church records and caul lists would be worthwhile .      I have spent a small fortune on Scotlandspeople and  I would really appreciate any suggestions in how to progress beyond this stalemate.    There numerous McAllisters in Dumbarton/Stirling so possibly they are interrelated but without proof I am totally stuck.           

[sancti]

Where does the 1841 census say John was born?

Where did the info on John's marriage come from?

[medhist]

The census says he was not born in Dumbartonshire. The marriage is from the parish register of Kilmaronock.

[sancti]

Confirmation of the marriage is on SP

10/08/1798 MCALASTER JOHN and ISABELLA FERGUSON at KILMARONOCK (DUNBARTON) /DUNBARTON

No baptisms showing for their children

When and where did the son Alexander die?

Added

Is there any additional info stated in the marriage record?

[medhist]

No baptisms by that couple anywhere in Scotland on SP. Alexander died 193 Castle Street, Glasgow 5 Mar 1874. That's the evidence for his parents.  Is it likely that baptisms would have been recorded in Free church records?

[medhist]

Regarding KIlmaronock marriage it just says Both in this parish. Neither are baptised there.
Regarding the marriage of George and Margaret McAllister it states they were cousins.

[sancti]

No guarantee that they were recorded at all. Many parents didn't bother or couldn't afford it and even if they were baptised, some ministers didn't record them.

What was John's occupation on his marriage record and the census record you found? Is Isabella still alive in 1841?

[medhist]

No occupation given on marriage record.
Census has him as a Chemical Operative in Dalmuir Shore. Most of the family worked there in that census. Dalmuir Shore was apparently pulled down in c1860 which is why they moved to Glasgow.

[medhist]

No sign of Isabella in census. John is living with son Alexander's family.
A Mrs McAllister died at Dalmuir in 1836 but several other McAllisters in parish so no way of knowing which one. No sign of either John or Isabella after 1841