"Dans un monde plein de néant" means "In a world full of nothingness"
"Quel dommage, mes yeux sont des sources claires" does mean "What a pity my eyes are clear springs"
"Même les promesses sont du vent" means "Even the promesses are just hot air" =false
"Ne me quitte pas encore" may mean "Don't leave me again" or "Don't leave me still", the latter seems to be the right one here.