I am not so sure that S&C is the culprit for Arwens MVD. Usually MVD is a congenital problem. Sure, diet can aggravate it. It's very possible that this would have shown up no matter what she was fed.
I would for SURE add water to all of her meals from now on. The S&C and ALL other freeze dried foods are concentrated. They are meant to be rehydrated to canned food consistency and not fed just dry out of the bag. The nutritional content between dry and water added would be significant.
Raw fed dogs labs can differ from kibble fed dogs, but it usually BUN and creatinine that are elevated, not liver enzymes.
I'm so sorry this happened. So sad when our babies are sick.
I am not real familiar with liver shunt and MVD diet recommendations, but I would definitely look at a supplement like denarmin and/or milk thistle - in addition to a low fat, low protein diet. I think that Dr. Dodds has a liver diet? You could google it. I would also seek the advice and knowledge of others who have dealt with this. Yorkies are very very prone to liver shunts and MVD so that group of folks would be great for info. They have a forum called yorkie talk dot com. Also yahoo groups has a liver group for impaired dogs that would be helpful as well.
Good luck and keep us posted. I know how worried you must be.