Thanks Pierre.
I guess the explosive capacity now is less per head of population than in the early to mid 1960s (the first recoding of the song was made while Flanders and Swann were touring the USA and Canada in 1966-67, but Flanders had sung it on stage (and probably on TV) in England before then so my best estimate of the date it was written is "somewhere between 1961 and 1966"). In fact the total capacity is probably lower than then - the number of warheads is about a third of what it was then and the reduction in strategic (high yield) warheads is proportionately more than the reduction in low yield (tactical weapons); so I would guess the total nuclear destructive capacity is now less than half of what it was in 1966 (but still ridiculously large).
I agree with all your corrections, except perhaps the last one - Flanders may have intended to say "to do unto him as he does unto me" instead of "do unto others as thou wouldst they do unto thee"(that's the version in the King James Authorised Version of the Bible, if my memory serves). I shall think about that for a while, and then either change it or not change it.

I think you might like the Flanders adaptation of La guerre de 14-18, it's nothing like a translation of the Brassens text but somehow seems to be absolutely faithful to his ideas. See https://lyricstranslate.com/en/michael-flanders-war-14-18-lyrics.html (I placed it as a separate song rather than as a translation since that seems to be done not only with with good different language adaptations but also with some almost literal translations).