Dog with cushions disease and stomach problems

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At 4 weeks recovering from a bout of vomiting and pink peeing my 12 year old schnauzer mix vomited last night undigested rice and chicken along with the cushions disease med the vet put him on. He had been recovering and this is a major setback. He is lethargic and falls if he tries to walk, has trouble using back legs. Stomach is not bloated but vibrates. A month ago X-rays, blood work, urine tests were done to the tune of $700+,  they were trying to see if he had a stone, blockage, etc. one cancerous cel showed as well as bronchitis possibly from aspired vomit, vet said not enough to call it cancer at one cel, they put him on antibiotics, anti nausea and colon inflammation medd and later on cushions disease meds to level a couple of liver enzymes that are off and treat the symptoms.  After spending all this I still don't know if he has cancer. In the last year weird grows have appeared through his body, these feel like moles, also black freckles.  He is no longer peeing pink but lingers squatting  in position as if waiting for more to come out. I'm devastated to see that he is clearly in pain. I called vet and all offered is more nausea med.  I think there is something else going on here. Does anyone have any clues as to what is ailing him besides cushions?  Thank you!