True, he knew the consequences of his actions and what he did was interference, if Mac had been one of the bad guys he would have been killed in a snap of fingers.

If you take the Watcher's premise seriously then what Joe did was a huge crime, so seeing it from the other side would be a nice thing.

About Methos' age that would so funny if that was what had happened to his age... a Watcher that is from that culture was writing his chronicle and puts that Methos is "5,000" meaning really old and everyone gets confused