Please help me prolong Squidward’s life

This is my precious boy and I recently found out he has chronic kidney failure despite being 1 year and 3 months old. I’m devastated. He always had pretty low energy but within 1-2 weeks out of nowhere he declined FAST. I was in the middle of closing on a home and moving into it so a lot of it went unnoticed as I thought the behavior was attributed to several other factors. Then one night he was just staring at me and I knew something was wrong immediately. I pieced everything together and got him an appointment immediately.

2 days later the lab work comes back (last two photos) and I felt sick. The vet had wondered if it was possibly Addisons so I brought him in the following day to be tested for that and it was negative. So she told me we needed to start treating his kidneys and that he needed to be on fluids everyday for the rest of his life. I began this treatment but due to being unimpressed by this vet (didn’t even check his mouth when I explained that we saw a black spot on the roof of his mouth and his breath was HORRID. Among many other negligible things), I decided to get a second opinion.

I went to a feline specialist and she gave him a scan which showed his kidney to be smaller than it should be. She said it’s likely he got into something toxic and it caused permanent damage. I was extremely cautious and careful about any plants, etc., he also NEVER gets into anything. He doesn’t even care about human food so I truly have no idea what it could’ve been. I adopted him at 5 months so maybe it was before then. I don’t know. The vet said it COULD be congenital but it’s extremely rare in young cats. However she did run a UTI test on him (since the first vet didn’t), and it was positive. So we treated that and he’s been on 100ml everyday since and apparently will be for the rest of his life.

He’s improved significantly but I’m still terrified that I won’t have much time with him. The vet said since she only sees this in older cats , the treatment is typically sustainable for 2-3 years so it’s unknown how long he can manage due to his young age. I have him on a renal diet (as much as possible but he’s kinda picky and demands his high protein turkey pate sometimes). I just want to know how I can improve his health, quality of life and hopefully extend it to be longer than just 2-3 years ):

The vet referred me to a renal program through a university in hopes they could provide more help but unfortunately they said an exam would be 4-6k and potential dialysis would cost 10-20k which isn’t attainable. If they were guaranteed treatments then I’d do everything in my power to save up but sadly they aren’t. I can’t lose him anytime soon. I’m begging for any guidance. Thank you