The problem with septicemia is that ongoing infection is likely to cause damage to internal organs.

The kidneys and liver will be the first to go. From there, heart issues can pop up, but even before then it is too late for a recovery. We just don't have liver transplants and kidney dialysis for snakes. You already suspect liver disease anyhoo.

This is a very old snake with lots of problems and the likelihood of internal organ failure in the near future. I'm certainly not going to fault anyone for trying everything to save the snake's life, but it is worth considering the amount of pain the snake is in.