As I have said, the laws of war were actually quite vague on some points. The local population having killed soldiers could be shot or hanged as brigands. De Martens, at least gives no indication of how guilt is to be attributed, he seems to be thinking only of men taken with weapons and has nothing to say on the punishment of whole villages or towns. 'Except in the case of reprisals' appears as an execption to practically every rule though.
Where orders were given to burn a town in reprisal, I think the usual assumption was that the inhabitants were allowed to leave first and that deliberately burning women and children alive would be an atrocity by anyone's standards. The chances of anyone getting punished for it in a situation of active hostities was rather low. If there was an officer in charge I suspect the incident would not be fully reported.
The killing of sleeping soldiers is unsporting, but to the practical peasant mind the best time to kill an enemy is when he is helpless. One might want to know whether this particular band of soldiers had already done harm in the area.
I hope you are not asking me to define Right or Wrong in this situation! I am neither a theologian nor a lawyer.
regards,
Susan