The chances of the safety chains breaking or (both) coming loose, I believe, are slim compared to the chances of a hitch failure. At least with only a 2000# trailer.
I set up my break-away cable to be slightly shorter than the safety chains. If the hitch comes away from the ball I would like for the brakes to apply on the trailer. I don't believe the chains would give way and a suddenly loose but still attached trailer would be a hand full.
Hopefully, in the event of such a emergency, the trailer brakes would apply whether the safety chains are still attached or not. I really believe it's the only chance of maintaining control.
Removing a hand from the wheel to apply the trailer brakes and/or stepping on the TV brakes would be shortening my odds of coming to a safe, controlled stop. In fact I would be more likely to step into the throttle since my TV far out weighs my trailer.
That's just my opinion.