I know it's often difficult to get them to spend 5 minutes with you answering questions in language that you understand, but insist on it
level of 400 is extremely high. If your father has
been in the hospital for 3 weeks with liver failure and his ammonia is still this high, it sounds pretty grim to me. Of course, I'm basing this on very limited information, and your father's doctors have the whole picture in front of them, so again, talk to them.