His cirrhosis and erectile dysfunction are probably unrelated. The problem with erectile dysfunction is that once he starts to loose it the next time he wonders if he will loose it. This is a normal human reaction. However, it does, or certainly can, block messages from brain to penis resulting in the collapse of erection. Before trying Viagra or Cialis it is always worth trying to de-emphasis intercourse, just enjoy each other's bodies then, in a week or so you take over while he just lies there and does nothing.
Sounds like a question for the mens health forum, or sexual heath forum. He should discuss it with his doctor as well. Good luck