good luck with this.. i have been in your shoes, it was almost too late for my girl. but she had her surgery more than a year ago and all symptoms have passed and she has more energy than ever.. i would definetly do the scintography, it is the best. i too had the ultrasound.. waste of money. i was also on the group that someone mentioned. the people on there are VERY helpful and they will help you get through this.. as far as your babies symptoms, those are pretty serious. my girl was the same and one day, she was completely out of it.. had to be rushed to the hospital and had her life saved.. she actually died and was brought back to us, followed by an hour of seizures.
anyways, i'd get your baby help asap. i wouldn't give him any chemicals, etc.. and very low protein.. again, livershunt/MVD group can help you with ALL your questions, concerns.. once the surgery is done, you will not believe the difference it will make. you will think you have a new dog
good luck, prayers for you guys!!