Great translation just a few technical errors
I am a Cro-Magnon => Unless one was really into archeology and ancient history, no English speaker would know what this meant, Better to just use caveman.
I go round in circles => The correct idiom would be "I run in circles" or even "I'm chasing my tail."
I am a man plenty of ambitions => I am a man full of ambition or I am a man with plenty ambitions
the king of the fools => the king of fools
Pure convenience good => goods
The world master, and behold what I've done with it => World master doesn't really make sense. You can say I rule the world and behold...
The men's land that men forsake! => The land of men that men forsake sounds better :)

When will I learn not to click 'thanks' until I've saved my comment :)

Instead of "a lion heart," "a lion's heart."

Instead of "I go forth, go forth backwards," "I advance, I advance backwards." Go forth doesn't imply making progress in the same way that advance does, weakening the paradox of
"avance à reculons." But your choice is not technically wrong, it's just a matter of opinion about style.

"Prisoned heart" is an accurate but very archaic way of translating it. Nowadays we would say "imprisoned heart."

Instead of "convenience goods," "consumer goods."

"The land of men that men forsake" is ambiguous because 'that' can refer to persons, things, any case, and singular or plural. If it's the land that's forsaken, "The land of men, which men forsake." If it were the men that were forsaken, "The land of men whom men forsake."

"Sur la terre, en toute saison" should be "On the Earth, in all seasons" instead. It rings better and is literal to the translation.

"I am a singular man of millions" would be better than "I am only one, then millions" in stanza 2.

"Mais mon compte est bon, mon compte est bon" thanks for the wonderful translation, I am curious about this line, I have seen it translated so many different ways every time i see this song, it is a french idiom and why does it come out so differently for so many people?

thank you so much, this line has puzzled me for a long time because I have seen it translated so many different ways. it is great to finally know what it really means. :) Okay I see now I had seen people translate this literally which really it has more meaning than that.