D3Hockey,
I concur with some of the others in recommending that treatments be stopped until this is sorted out. To me, this seems like a very unfortunate example of what is sometimes wrong in the prostate cancer treatment community. If I understand the scenario correctly:
1. The healthcare provider knows your insurance refused to pay for the treatment.
2. The provider knows it will be financially ruinous to you, without insurance.
3. The provider, as an expert professional in the treatment of prostate cancer, knows there are many efficacious approaches (possibly including active surveillance) for low-volume Gleason 6 cancer that are lower cost and would be covered by your insurance.
4. The provider chose to treat anway.
That seems likely ethically shaky ground on their part. I would be very assertive on achieving a successful resolution.
Good luck. I know this really roils you and your husband's emotions at a difficult time.