your post touched my heart. so sorry your brother is not feeling well...and you're a good sis to be so supportive.if your brother is able to work is he aware of vocational rehabilitation in your state? he may qualify for job placement due to his diagnosis, plus receive good counseling.
as for losing his job due to poor performance due to his illness i'm not sure but i think he may have some ground to stand on under the american disabilities act. google it and see if it applies.
also he may want to apply through social security for ssi. it will help with his meds and give him a small monthly money amount.
hope this helps. wishing you and your brother a blessed christmas together.