Sounds like you have made a good start, you have a fair trail back on the Canadian side. But for anyone here in Scotland to help, you're going to have to track the Canadians right back to where the first immigrant appears (Robert, if I've read your history correctly). If you can get his death certificate, then hopefully it will have his date and place of birth on it - even a DOB would be helpful, as you could then log on to
General Register Office for Scotland and try to find his birth certificate. Scottish birth certificates contain not only the parent's names, but also the date and place of their marriage - which will lead you to their marriage certificate. These list the names of
their parents and whether or not they were still alive at that date... all, of course, assuming these events were post-1855. Events earlier than this are logged (hopefully) in the OPRs or Old Parish Records.
You have a bit of work ahead of you but best of luck in the search. I'm sure that other Canadian posters here can assist with sites containing ships records of immigration etc.