QHORIN HALFHAND, UNWAVERING RANGER: SACRIFICE FOR THE CAUSE

Can Qhorin's Sacrifice For The Cause Ability stop Mag The Mighty's Chieftain's Fury?

Yes.

If I cancel the effects of "Sacrifice for the Cause", is Qhorin's destruction also canceled?

Yes, its destruction is part of the ability.

Follow up: Can Qhorin's ability be used next Turn?

Yes.