Good Morning. In April of 2018, I too was diagnosed with cirrhosis of the liver, and I too experienced this, and still do, but I was just diagnosed with vitamin D deficiency, and now am taking vitamin D once a week, (50,000ng), my doctor and pharmacist seem to think this will help. I am praying it will.
You best be would be to ask his doctors. Sleep reversal is a symptom of HE and as you probably know is a symptom of cirrhosis. Sleep medication is problematic as it could exacerbate the HE.
With advanced liver disease your best source of information is his medical team.
Has he been evaluated for transplant?