Technically the chief's line is descended from a Kilpatrick. Sorry,I know this doesn't answer any of your questions; I guess because there is no satisfactory answer.
I suppose that's as good an answer as there can be. As long as the Colquhouns realize that it's Kilpatrick blood that made them what they are.

I guess you know that Kil/Kirkpatrick has it's own crest and I think their own family tartan?
I have seen the crest and such (my grandfather had it on the wall before he died, and it went to one of my brothers). But I've never seen or heard of a Kilpatrick tartan. That would be very cool if there were one! If you have a reference to one, please share it.