it appears that he did everything right & saved the aircraft from even more damage
Absolutely! A very experienced and accomplished P-51 pilot in my view.
It was just unlucky that he had chosen to land on the grass runway rather than the concrete - the original runway was truncated by the motorway development and the threshold is more or less at the hedge...
That taxiway lip should be built up to avoid further occurrences - a B-17 did something similar after inadvertently landing short some years before but, with power available, was able to sort the bounce out.