Hi there both of you

Captain2 has certainly found lots of info there for you.
Ancestry is not however the best way to delve in to Scottish records, although it is the best for the Scottish Census transcripts.
With all the info that Captain2 has now found, you need to look at the pay to view site
www.scotlandspeople.gov.uk Although pay to view, costs are very reasonable...hurray! Scottish BMDs are some of the best in the world. For this period you are looking at, you can view Gilbert's birth registration online. His birth cert will include his parents' marriage date and place. From there you can work back and forward really with confidence.
Don't worry about ages showing on censuses. Always variable for people really. In respect of addresses, as you mention, really common to find people moving up and down a street, renting accomodation as they did.
Monica