[1] The song uses the verb "halten" in may different ways (prefixes, etc.) that cannot all be translated with the same verb in English so most of the repetition is lost in translation.
[2] The chorus was inspired by the song "Die Moritat von Mackie Messer" ("Mack the Knife") from the Die Dreigroschenoper (The Threepenny Opera) by Bertolt Brecht and Kurt Weill.
Part of the original song:
Und der Haifisch, der hat Z탤hne
Und die tr탤gt er im Gesicht
Und MacHeath, der hat ein Messer
Doch das Messer sieht man nicht
And my translation:
And the shark, it has teeth
And it wears them in its face
And MacHeath, he has a knife
But no one sees the knife
[3] "Z탤hre" is an archaic word for "tear", even more closely related to the English word than the usual German word, "Tr탤ne".
[4] "Schadlos halten" is legal terminology that means "to hold harmless", "to indemnify", and so on, but that doesn't seem to fit here.