Partis means “factions”, so “spouses” seems an excellent choice of words since factions were made through alliances and marriages. In the translation of songs and poetry, prosody has to be taken into account (“spouses” rhymes with “glasses” and “lilies” – the lily was the French symbol of royalty).

Chantons en vrais amis literally means “Let’s sing as if we were true friends”.

Ce diable à quatre would probably need a FL question by itself. We expect something after “quatre” but it is cut short probably to keep the rhyme (quatre/battre). I have found a presentation of this song in a teacher’s guide and it says that Ce diable à quatre means coquin* (a seducer) which is in keeping with the “vert galant”. I would say translating by “fourfold devil” is just as obscure as the French diable à quatre.

* Coquin can also mean “scoundrel” – but that’s not what it means here.