Phil wrote:

(snip)

More significantly, the breeder stated to us that the cat has urinated
outside the litter box on occasion during the 5 years she had her,
from kttenhood, even urinating on her directly.

Sounds like this cat was used as a breeding queen. It's not unusual for
overbred females to lose muscle tone and to have difficulty with
incontinence. This poor girl is facing death because she was misused by
a breeder.

Since you mentioned unusually large quantities of urine, make sure the
vet has checked for diabetes. Abundant urine is a classic symptom.