Urgent Advice Needed: Is it time to euthanize my rabbit or is there still hope?

Species: Rabbit

Age:8

Sex/Neuter status: male, neutered

Breed: Netherland Dwarf Dutch mix

Body weight:1.36 kg

History:

I adopted Chico from a shelter when he was about a year old. As he got older, I discovered he has kidney issues, to the extent I did not know but he's seemed content for our time together. We've been to the vet a few times on the occasions where he didn't eat/drink/urinate/defecate for a day, and after I being given one feeding of critical care, he gets back to normal. As he's gotten older he eats less and less hay, and instead is eating more and more pellets (so he essentially is always eating his pellets). Additionally over the course of the last few weeks he's been urinating larger amounts, and I mean puddles.

Back story:

I woke up yesterday morning to let him out of his cage, and he didn't come out. He normally hops around all excited but throughout the day he did not come out of his cage once, he was teeth grinding a bit, and very lethargic. He didn't eat his food from the night prior and he didn't seem to be pooping or peeing either, I thought that it was okay and maybe this was a one day thing like in the past so I let him sit for the day to see how it panned out.Throughout the day I noticed he was lying down more than usual and come night time nothing had changed and I realized I had a real problem on my hands. He was shaking his head a lot, labored breathing, teeth grinding more and when he did hop out for the first time of day at 11pm, he was almost dragging his feet behind him. I ended up feeding him some critical care. 30 min later, he was having trouble keeping himself upright, his front paws kept on sliding outwards on the hardwood floors of which he's mastered over the last few years. I called the vet, and made an emergency visit at 12am.

Vets diagnosis:

The vet I had went to I had never gone to before but I gave her as much info as I possibly could. She put the pieces together of which none of the other vets I've visited have done before. She stated:

• He was really skinny, for the amount he was eating leading her to believe there was an underlying issue
• She performed an ultrasound and found that one kidney was more or less likely a fluid filled non-functional cavity, and the other (probably the functional one, but who knows), was filled with nephrocytes -She said E.cuniculi could have been a culprit, working in tandem with the original kidney issues -Also stated he has mild arthritis, and could use some dental work but not bad

Treatment recieved:

fluids, pain killers (Buprenorphine) , and panacur for the potential of E.cuniculi, and he is still on critical care (She also suggested bloodwork, but in all honesty I am a student. I want the best life for my rabbit, but considering how old he is, I feel as though blood work would at this point be more for me having a peace of mind than for him)

Issue:

It has been 20 hours since his first dose of everything and it seems as though his condition has gotten worse. It's almost as if he can't bear the weight of his own body as he hasn't stood up the whole day, he lies down with his head on the floor regardless of what its on and his positioning looks very uncomfortable. Every hour or two he maybe moves to another spot in the room but struggles to do so, His head bobs up and down when he tries to get it up and he slides everywhere even though he is in his cage or on carpeted floor (both are more grippy than the hardwood)almost like if hes dragging himself, but his front paws are not helping all that much. If I pick him up, hes like dead weight. He hasn't urinated at all, and his feces isn't consistent. He still isn't eating/drinking and I'm still feeding the critical care. The teeth grinding and head flopping have stopped but it pains me to see him like this. I don't know if its worth it to wait to see if the panacur works (on day 2 of treatment now), of maybe if I should go to the vet and ask them to put him out of his misery? If I do wait for the panacur, I was curious as to what I should be expecting as aftermath (e.g. paralysis, neuro issues?)

Thank you very much for any advice. I'm really struggling here.

edit: He's starting to get a slight head tilt as well