Just concentrate on fluids tonight. The tube goes down the duck’s right side of his throat, avoiding the airway (trachea) at the base of the tongue. Do you know how much he weighs, or can you weigh him while holding him, then weigh yourself, and subtract your weight? A kitchen scale works well for most poultry. Fluids are given slowly at first to see if he tolerates it. 15 ml per pound 3-4 times a day is the liquids goal. You have given NutriDrench already, right? So no B vitamins are needed.
@casportpony , can you verify that? The grind up some chicken feed and blend it a lot of measured water. Tomorrow morning might be good to start food.