I would say that the performance of the simulator is a bit suspect- that pitch is out of line, but almost certainly you are too heavy to climb to FL410. You should see what the weight of the aeroplane is. My table for the RB211 powered 747-400 shows a maximum weight at FL410 of just over 250,000kg. With 70,000kg fuel, that takes you down to 180,000kg weight of aeroplane, crew, catering and payload. With an empty weight of over 180,000kg, add 6000kg fuel and catering (the crew gets very hungry), you are way out of the bounds of possibility! If you have anything up to 100,000kg payload, you are trying to push the aeroplane too far. For FL 370, you should be at a max weight of about 305,000kg.