1) It's a connection. However, most anyone who recognized the tartan would assume you were a Cunningham, or at least a descendant of one. As for criticism, there's probably no way to predict it, or even to prevent it. For every person who might raise an eyebrow at your wearing of the Cunningham tartan, there's probably another person who will insist you're wearing the Ramsay tartan.

2) Clan and district tartans tend to be kept separate, but there are exceptions. A case in point is the Angus tartan, designed some time around the turn of the (20th) century. No one's really sure if it was intended as a family or district tartan, so it's used as both. (Note: Angus was known as Forfarshire at the time; however, the tartan might have been named after the Earldom of Angus.) The district association seems to be the most prevalent, however. On the other hand, the Campbell of Cawdor tartan was used as a district (and military) tartan for Argyll before it came to be associated with the Cawdor branch of the family. Now the family association has prevailed.

3) Campbells shouldn't mind others wearing the Black Watch tartan because, according to the experts on the subject (the late James Scarlett and Alastair Campbell of Airds), the Campbells wear the Black Watch tartan.