Don't know the answer to the questions about the testing.
My Scout had kidney disease. His last four months were downhill, starting out with two bouts of acute pancreatitis, which I think kidney dogs are more prone to. I modified his homecooked diet, but he didn't eat much. Then he let me know he wanted meat and only meat. I was horrified (low protein diet! pancreatitis!), but gave him beef and he loved every bit of it for months. He still kept losing weight, though. His time between urinating kept decreasing till finally it was about every 2-3 hours. He didn't want to use the dog door out back anymore; he was getting weaker and there were steps. I put human bed pee pads around the house during the day, which he would determinedly not use so I would put down more ... Finally the house was just one big layer of pee pads. At night I took him on leash out front (fewer stairs) and we had moonlight walks that I'll always remember.
He still barked at sounds of dogs walking by, and supervised all my activities. After the pancreatitis bouts were over and he started eating again, I did not see signs of pain. One reason might be I was giving him Azodyl, a dietary enzyme that is supposed to help decrease the toxins circulating in the blood. His creatinine levels did decrease significantly once he was on Azodyl. He and Nutmeg were very close, and they spent most of their time together. He just kept getting weaker, and finally I was having to support him with a sling getting up and lying down, and on steps. I scheduled him to be put down on a Monday, and spent all weekend crying. He always loved shredding up paper, especially used tissues, and he would struggle up and totter over to a wastebasket and start shredding the tissues where I was crying over him and give me his patented "What is your PROBLEM?" look when I protested.
On the day before the scheduled euthanasia, he had a very violent seizure and I couldn't bear to think of him having another one. I went ahead and took him in that day. I feel for you, Ducky. (((hugs)))