Can we really know how long my father has to live with colon cancer?

Hi there. My 55 year old father has advanced stage 4 colon cancer that is no longer in the colon but has taken over his liver and is in lymph nodes, some in lungs, and who knows where else. He has fought it for three years with every chemo possible and the chemo's no longer do any good. He won't accept that he is dying and is doing everything and anything to make sure this doesn't happen, even thought he knows better. He went to Germany and took my little sister with him, when he got there he got much worse, got a big belly from either a soccer ball sized liver or from fluids or both. He has edema in his ankles, his eyes are a little bit yellow, low liver function, and worst of all he is mean and totally out of it. He isn't logical anymore and doesn't care about his kids, which isn't like him. As far as I can tell he is in the end stages of liver failure, but since we couldn't get him to come home so we could take care of him, we have no idea if he is so bad he won't make it home. He seems so out of it, that he honestly thinks these bogus treatments in Germany are helping when the doctors don't even have any hope. I asked a doctor there what they thought and they said his life expectancy was one day to one year....that seems a little bit too big of a difference. And he must be bad enough to have said one day. His main doctor here says two to four months, maybe less now. Anyone have experience with this? I don't know how much more we can watch him like this! Thanks!