very interesting report.
The pilot indicated that he could not land because he was holding the door with his hand. This implied that the pilot was holding the door with his left hand and therefore could not operate the helicopter's collective control to adjust the rotor blade angle. To slow the helicopter to the point where he would be able to close the door, he would have had to ease back on the cyclic control with his right hand to raise the nose of the helicopter and bleed off airspeed. Without adjusting collective, the helicopter would climb in a nose-high attitude as observed.
The climb got progressively steeper before the nose suddenly dropped. The dropping of the nose is consistent with the pilot pushing forward on the cyclic control in an attempt to recover from the nose-high attitude. The pilot should have been aware of the dangers of mast bumping through the pilot's initial helicopter licensing training and subsequent experience with helicopter operations. It is likely that, in the pilot's preoccupation with the open door, he did not apply the corrective actions required to recover from a nose-high attitude. This allowed the helicopter to enter a low-g condition, which in turn led to mast bumping and the in-flight breakup of the helicopter.