I'm so, so sorry to read that your beloved Mystic is still not well. The second opinion is a good idea; is there an internist near you? Lisa's idea of money for his bill's instead of Christmas gifts is a good one. And I understand there's a site or organization online called "chipin" where you could start a fund and people could "chip in" whatever amount they could. I did something similar when Shadow broke his leg, and it was quite a help.

Prayers coming for you and Mystic, that he'll be restored to health.