rabies vaccine and crf? spike in creatinine level

My cat is 6 years old and was diagnosed with CRF about two years ago. We have him on KD diet. About a year ago, he got really dehydrated and the vet gave him Sub Q fluids and he seemed to perk up. Also around that time he had is distemper vaccine and seemed to have a slight reaction (stopped eating, lethargic) which I think triggered the dehydration. I decided at that time since he is an indoor only cat and because of his kidney disease to not vaccinate him anymore. Just last week he showed signs of dehydration again and slight weight loss. I took him to the vet and he did sub Q fluids. We were leaving for vacation and the vet said he would keep him there but wanted to do a rabies vaccine since he was overdue. He said it would be fine and shouldn't give a reaction. He also did bloodwork and his creatinine level was 4.6. He was eating fine also. When we picked him up four days later the vet said he gave the vaccine and on the third day he stopped eating and gave sub Q fluids each day. I took him home and he still did not eat, had some vomiting and did sub Q fluids at home. After two days of not eating we returned for another exam. He had developed ulcers in his mouth, his teeth had turned black and the vet did more bloodwork and his creatinine level jumped to 13 in one week. He is now left at the vet for more intensive continuous IV fluid therapy to help flush the kidneys. He wants to do more bloodwork on Monday. He said something must have happened for his level to jump that fast that soon perhaps a blood clot to the kidney or a kidney stone and maybe the fluids can flush it. I know there is no cure, but my cat is only 6 years old. I am hoping to get some more time out of him. He also has no appetite, the vet gave him some food in a tube which he managed to keep down and gave him meds to stimulate his appetite. He is still in good spirits and not depressed. My question is do you think the rabies vaccine may have altered his immune system and made his kideneys worse? Also, have you seen cats with numbers this high bounce back?

Rex did not make it. We got a call from the vet early this morning that we needed to come say goodbye. I don't know how this happened, it is just killing me. I miss him so much. I wish I could just go back in time and say no to the vaccine or cancel our trip. I really didn't think he was in that bad of shape two weeks ago. The vet said he would be fine and I trusted him. He was on IV fluids since yesterday to help flush his system and was supposed to get more bloodwork tomorrow morning to see if it helped. The vet called us early this morning and we met him to say our goodbyes. Rex could barely move and was practically gasping for air. I was happy that I could be there with him during his last breathes, but now I feel such an emptiness in my heart and that I failed him. Thank you for your condolences.