Hi Michelle
It is easy to go off course when you are researching and you are right to want to verify your steps along the way

Am I right in thinking that the addresses for residence on all four certificates, including the marriage matched?
Did the parents' names match for Francis Ballantyne on his 1857 marriage cert. and the death details that have been found in NZ?. It might also be worthwhile trying to find the 1860 death entry, if you can, for the death of young 'Mrs Ballantyne' during the voyage to NZ to confirm what you can for her parents also.
Francis' 3rd marriage to Elizabeth in NZ also gives you another opportunity to confirm his place of birth and parents hopefully.
The Scots liked their name variants and can confuse you if you are not familiar with them. This site is good for giving you an idea on name variants
www.whatsinaname.net.
I would not be so concerned about ages for Francis. People's ages do vary, mostly down

. You are lucky to have so many fact verified in NZ about him. Also in Scotland the name Francis Ballantyne is quite rare and his family has been well researched.
Good luck with everything.
Monica
