I never heard of a vet not wanting to put a pup on steroids due to "other problems" they will cause. .... with that albumin I would think he would be on steroids!!
It sounds like protein losing enteropathy and she is right...you will lose him if it keeps dropping.
Two weeks of diarrhea is scary enough.
PLEASE get him to a vet who can diagnose and treat this. My pup was started on IVs and plasma for a low albumin.
She was put on prednisone and metronidazole.