Radiation for Louis' brain tumor

A few weeks ago Louis started tilting his head. I thought it was just an ear infection but it wasn’t going away with medication. He started falling a lot and seemed like he wasn’t feeling well. I was able to get him in with a neurologist. They did an MRI on him and gave me the worst possible news. He has a tumor in his brain. The doctor said it was cancer and inoperable. I am totally devastated. Those of you that don’t know, Louis is only 3 years old. He goes everywhere with me including to work. The doctor said we could try radiation and he thinks Louis would be a good candidate because he responded so well to the steroid medication they gave him. Louis does have insurance but I don’t know if they will cover any of this. The MRI alone was $5000 (which I had to pay for up front and then submit to insurance with no guarantee they will pay). An appointment with the radiology/oncology vet is $250 just for a consult. Before anything though, they need to do blood work and a CT scan. The radiation and CT scan is another $16,996.18. That brings the total of this tumor to $22,140.45. Louis insurance max annual payout is $15,000. If they approve his claim that will leave $7,000. I’m really horrible at asking for help and am so uncomfortable doing this but several people have been urging me to set this up and it’s really a matter of life or death for my sweet Louis.