That is a tough place to be for sure. Glad to hear he is eating. We cared for foxers many years ago; our oldest girl lived to reach over 11 years. Luv dem foxers!!
This source may help if he has a head injury; best given soon after a head injury.
https://www.amazon.com/VeganSafe-B-1...NsaWNrPXRydWU=
This source in particular is the bioidentical form of B12 that the body of mammals recognizes and is able to utilize best. It is a extracted from an organic source with no sugars or sweeteners added, tastes tart sweet, which squirrels like.
(see my thread on Vital Nutrients for more info on bioidentical vitamin forms)
Recommend the (2500 mcg.) bottle be used to support a reduced dose for a squirrel, since the amount noted on the label of the other version this company also offers is too high to reduce for the targeted dose for an adult squirrel.
Using this source only: 1 needle drop from a (1 cc) (1 ml) needle syringe onto food daily for the first few of days.
If then he improves, then reduce the amount to 1 needle drop every other day for two weeks.
(try adding it to 1/4 Tsp. of organic naturally sweetend applesause)
Should you have any questions on the dosage please send me a PM.
Take care friend. DF