I only signed up yesterday, and I've already realised I may as well set up camp in the corner and just READ!

I have a few little niggly things that I figure I'd get other people's opinions on. It's not that I haven't tried to find the answers myself, it's more that I don't think there's a definite answer that would put them to sleep once and for all.
Firstly, the family I am looking at is Christie. We've still got a way to go, but for amatuers, we've done pretty well to get things backwards compatible from present day to about 1780's, and a comment I read yesterday said something about the writing on Census records, so help me, them Wills! I thought I was Shakespeare reincarnated trying to read them!
So, long story short. James Christie is the father, and James Scott Christie is the son that came to Australia as a convict in 1842. A letter states that James Christie was a Scotchman Edinborough. Records we have so far have placed him in St. James, Westminster as early as 1816. His death certificate puts him down as being born in approx. 1782. (Possibly married Elizabeth Hall in 1815, but not confirmed yet).
James Scott Christie was sentenced to transportation in 1838, which coincides with the year his father died, and he was kept behind because he could read/write and helped the ships surgeon.
3 questions:
Was it common for families with a Scottish background to put the Scott into their names, or is this more than likely from someone who married into the family along the way?
James Scott Christie was charged and sentenced in 1838, but was charged again in 1842. (Old Bailey records)We found him on the York Convict Hulk in the 1841 census as well. Was it more likely that he conned his way off the ship, or was he allowed to roam around, work etc? (Charges did include forgery, and the 1842 case also mentions the prisoner as working for someone earlier in the year, even though he'd already been sentenced to transportation)
We have insurance records for James Christie, showing him having a business in 1816 - 1832. His death certificate puts his age at this time as approx. 34 in 1816. Yet, after he died, his wife, Elizabeth, was left £60 a year, due to James Christie being a 'paid out member', from the Calton Corporation (Edinborough). We found Calton in Scotland, but haven't been able to find any mention of the Calton Corporation. Has anyone else had an experience where there was 'paid out membership', or money left to others from one?
Logically, and with nothing more than assumptions to back it up, it was something that James contributed to over the years. As he was working in London for all that time, maybe the corporation was set up in/around England, and Calton in Scotland may have been where the corporation originated? or if he was born in Edinborough, could he have started contributing in some way, before moving to England?
He was also a Deacon and Treasurer at Wells Street Chapel (Wells Street Scotch Church?), Oxford Street, London and buried at Bunhill Row Burying Ground. We didn't find any records of James Christie at Bunhill (free lookup on National Burial Index), so could the Calton Corporation have something to do with him being Nonconformist?
Would love other people's opinions on what they've found with their own experiences in similar matters.

I love researching the family tree, but wouldn't it have been nice if someone had left a diary explaining everything!
Victoria