Not knowing anything about them, I thought the Bourchiers would turn out to be Huguenots. Not a bit of it. They have a huge English ancestry. One of them married Oliver Cromwell. I don't think I'll get past the Wikipedia pages on them for a bit. But it might be possible to find out what Elizabeth's immediate kin were doing at the time of her marriage.
I think there's just a possibility I may have Alexander the saddler's father's date of birth, thanks to an online partial transcript of the Inverness register by Jane MacGillivray whose main interest is MacGillivray connections. She has also done work on the Petty register, also online. IF it is the right John MacIntosh his father was a James, and brother to Mackintosh of Holm, a smallish Inverness landowner just to the south of the burgh proper, whose family certainly did have MacGillivray connections, and who were involved in burgh affairs over a number of generations (and also in the Darien settlement in Georgia at the end of the 1730s). But it might be a little time before I can confirm (or not) any of that. If it does turn out to be right there might be some difficulty explaining how the Clarks came to be connected. Their mother was, I think, a Mackintosh, but my impression was that she was likely to have been of the Dalmigavie family. But that bridge will have to be crossed when we come to it.