Help me save my Winter

On Thursday night I came home and noticed that my winter was less active than he normally is, he stopped playing around, stopped using the bathroom and ate at minimum. By Friday I noticed he didn’t get any better, in fact he stopped eating and drinking water and stayed in one spot all day. I called all my local vets and they all turned me down due to financial reasons, so I turned to aspca which they also ended up turning me down because they told me my cat wasn’t an emergency. Saturday morning comes and that’s when I decide to take my cat to aspca because a man told me it’s better to just walk in, nurses didn’t even bother looking at him and instead told me to go elsewhere. So I went to the Kew Gardens animal hospital where they finally saw him, they took blood and ran xrays and even a CBC test. Winters result came back that his red blood cells were really low and his body is failing because he was severely anemic, so he told me winter needed an immediate blood transfusion.the hospital that I was currently in did not do blood transfusions in their hospital so they suggested me to the nearest partnered Vet which was BluePearl Vet.. The CBC and blood that was taken from the first hospital was a little more than 500.00 which I paid. When I got to the second hospital they immediately took winter from me because he was panting and his gums were white. They ran tests on him for felv and leukemia, he came back negative for leukemia but came back positive for being anemic, severely anemic. The doctors can’t figure out what’s causing him to be anemic so they told me they need to keep him at the hospital. I deposited 2,065.35 to keep winter for 24 hours under hospital care, but the doctors are telling me that it is urgent for him to stay for another 3 days which would bump my bill to +4000 estimating around 6k which is way far out of my budget. The doctors basically told me if I take him home tomorrow I could be taking him home to die which I don’t want, I want to help him and make sure he lives a long and full life like he deserves, Please help me save my baby he’s not even two years old.