Beagle suddenly sick...

Last tuesday he got into the garbage and ate a package of expired hotdogs. My sister found the package so we know he didn't eat that. He later puked the hotdogs up and ate his puke. After that he was fine and acting normal. Then last friday he lost his appetite and was very lethargic and acted like he was dizzy. We started giving him pedialyte via a syringe and feeding him pulled chicken mixed with this pumpkin supplement we bought at petco. He was still active but not himself. We took him to an animal hospital and they said he wasnt dehydrated and gave him amoxicillan and sent him home. He later had a seizure and we rushed him to another vet. They started him on fluids and started running tests. His BUN and potassium are high. Their machine only goes to 130 and it says its greater than that. He's been on fluids since monday and weve taken him home each night. Hes still very lethargic and not himself. We know its not lyme disease, its not an obstruction either. The xray showed everything is normal. They could see one kidney clearly and it looked normal. Today we noticed he had trouble seeing so my sister took him into the vet and they tested his blood pressure, its high so the vet put him on meds. We take him back for blood work tomorrow to see if its improved. His eyes are bulgy so the vet took a pic and is getting an ophthalmologists opinion. She said kidney failure is a possibility but hes having so many other symptoms she cant narrow it down. She gave him a steroid in case it was addisons disease but he didnt respond to it. She gave him a high dose of antibiotics in case its leptosporosis but we tested for havent tested for it yet. Has anyone seen anything like this? We're at our wits end, this came on all of a sudden we just want to make him better! The vet says she stumped and at this time we're running tests to rule things out.

His symptoms are: His symptoms are:
Loss of appetite
High levels in blood
Tired
Weak
Dizziness or disoriented
Loss of vision
High blood pressure
Loss of interest

We got him 7 yrs ago, the vet thinks hes 10 or 11 yrs old.