Im not an expert on pacmans but from what I know about MBD Id say that its a pretty bad case and as far as a vet trip I dont it would be worth it. It looks like its to a point where even a vet couldnt help. Ive seen some pretty bad reptiles with mbd and at one point even found a home for a bearded dragon who had pretty bad MBD. Im very sorry you recieved him like that. Even if you start dusting his food I dont believe it will help your Bowser much. And again Im sorry that you recieved him like that. Poor guy