My father was recently diagnosed with stage 4 cirrhosis alcohol-related and in the last 3 weeks two different times now they've had to pull over 6 l of fluid off his abdomen how late stage is it when they have to pull that much fluid that often?

That is advanced liver disease. He should be under the care of a liver specialist. He should avoid alcohol and medications that are primarily liver metabolized. Is he a transplant candidate? If so, he should also be seeing a transplant doctor. There are medications to help control the fluid in his abdomen (ascites). Good luck to both of you!

Stage 4 designates last stage of cirrhosis with rapidly reaccumulating ascites worrisome for rapid decompensation. You should have a discussion with his treating doc regarding best ways to provide comfort, considering having a intraperitoneal catheter and realistic expectations.