I was curios about the length of the snare, because if a yote can build a little steam before hitting the end, he can generate a lot more force. Attachment height is another factor, the higher the snare is tied off, the less force the coyote can generate when it hits the end, more like a pendulum.
This may sound dumb, but are you 100% sure it was a coyote in both cases? I know you have snow on the ground but I am also figuring you set on an established trail, which could be used by both coyotes and deer.
Another idea may be to use your forearm in the snare to see just how easy the BAD opens up. Not a scientific method by any means, but would still give you a better idea of how hard a critter would have to pull to open one.
RO