Really sorry to hear this - it must be very worrying for you.
Given he;s eating and drinking vritually nothing, you need to syringe feed 20-30ml (full stomach capacity) every 2-3 hours (time taken for stomach to empty). You might need to also syringe 5ml of fluid every hour if he is looking dehydrated.
There should have been an improvement within 5 days so you do need to return to the vet and a proper culture/diagnosis needs to be done.
Might be worth culturing the ear exudate (is there pus?) or sample from the nostril as sometimes it can be a bug resistant to baytril.
My Tia developed a sudden head tilt with pus in the ear and was found to have a bug that was resistant to septrin, baytril and zithromax and she had to have daily gentamycin injections for a week - which cleared it up great but was the ONLY antibiotic that killed the bug.
Theroretically pigs can get E cuniculi - but it is rare and would normally only be caught from an infected rabbit in close contact
Some info on the bug in rabbits
http://www.houserabbit.co.uk/resources/content/info-sheets/ecuniculi.htm
There are other more probable causes in Humphrey's case which is basically a respiratory infection that has developed into a middle/inner ear infection (or vice versa) that is baytril-resistant (think pseudomonas and/or you also need to rule out ear mites).
I would go back to the vets tomorrow and get cultures done and keep maintaining syringe feeding while you wait for the results which should come back by monday/tuesday. In the interim your vets might like to try a different antibioitic given that baytril is so ineffective and ensure you have gut stimulant medication for the weekend given his lack of food intake.
Fingers and paws crossed for him.
x