Use the warm mist. You don't have to put the vick tab or whatever in it, do you? Ours is a Vicks one, but we don't put anything on it. With a little one, I might smear some Vicks on a piece of cardboard and leave it on the nightstand. Don't know for sure how much that would help, but I'd do it anyway....As of right now, 2yo DD has Vicks smeared all over her chest and back and the vaporizer going full steam ahead, so to speak, in her room.
And for the congestion of your LO, put a couple of drops of breastmilk in her nose. DD2 is congested too, and while it was extremely comical yesterday when I tried to do that, it did work! Sorry your baby is getting sick.