Sorry I've taken so long to answer, had a crazy day at varsity! I'm so sorry Benson has AIHA

Atleast you have an answer about him though. Its vital that he is treated asap so that his immune system can be brought under control and the destruction of those red blood cells can be stopped. They'll probably put him onto high doses of steroids (pred is a steroid) as well as other drugs to protect his tummy. Please, please get him back to the vet as soon as you can to start treatment, its vital.
Steff is right, CIMDA is a great group with a wealth of knowledge and support to offer on immune mediated diseases. They're really great.
I really hope Benson will stabilise soon. Big hugs to both you and him!