Colby needs your help!

This is Colby aka Tiny Man. He was a stray, running by the river alone in a gravel pit for months. When we found him, he was so scared. He wouldn't leave our side in terror that he would be abandonded again. His fur was so long and matted, his nails were digging into his paws. His behind was so inflamed and impacted with feces we had to use diaper rash cream on him. We looked for someone missing him but never found anyone looking for him and he was not microchipped. I was in disbelief that no one was missing him! He was so little and adorable!  We decided he would stay with us and become part of our family, which includes 3 other dogs with special needs and 4 cats.  About 6 weeks after he came to live with us, we took him for a checkup at the vet, along with our other 3 dogs. He was vaccinated, heartworm tested and was given heartguard.  Two nights later, he started showing unusual symptoms. He would walk aimlessly for hours, fall, become disconnected and drool uncontrollably. It happened once so we thought it was just anxiety.  He was always walking, he never rested for long. We thought it was maybe just stray life. He had another "episode" a few weeks later, 2 nights in a row.  We called the vet and got him in for tests.  Liver shunt or epilepsy was suspected. First tests didn't show liver shunt so he was given phenobarbital for epilepsy. Seizure meds did great for 2 days.  On the 3rd day, he started having the worst episode yet. He was rushed to the vets office and further tests were done and it was determined he did have the liver shunt. We very nearly lost him. He was close to death but our guy pulled through.  He is now on a very restricted diet, prescription food and medication.  He may or may not live long like this, but we were told his liver will eventually fail. He is doing good so far but it can change anytime. To be well and live a normal life, he needs liver shunt surgery.  The shunt/vein is tied off and when it is closed, dogs can live a normal life!  We want this for our little Colby Cheese!  Help us help our Tiny Man! Thank You. ♡ Marcus and Valerie