do you have ANY antibiotics on hand? It sounds like you're at the last resort ... I think it would be very difficult to dose, but I think I'd try an itty-bitty dose of penicillin IM. Like maybe .1cc - that's POINT 1 cc ie: 1/10 of a cc. for four days.
Hmmm...well, bumblefoot is a staph infection. If the pus pockets (possible bumblefoot) on the feet are related to the lump in the neck - then you've got a very sick baby..ie the staph has become systemic. I do not know how to treat such a little one for this. Do some searches here for chick...