If Belegar gets angry enough, his "breaking point" will consist of him levelling the accusation at Thorgrim, and demanding recompense, as any wronged Dawi would. Either Thorgrim explains and Belegar withdraws the accusation, or Thorgrim pays him for the energy, or Thorgrim refuses to explain - and I do not believe that a canny operator like Thorgrim will let his Empire slip into civil war when he's aware of the problem.
Have a little faith in Belegar. He's not going to start a war on the spot. Have the barest hint of faith that the High King is similarly not a complete fool.
[x] Yes