It sounds the amount of beer he drinks is starting to affect your friend pretty badly. It could really damage his liver, especially when that amount, and the regularity of the drinking as well. I would recommend that he cut down on it, and don't drink as much.
I briefly knew a friend's husband who shook like that and he also drank a great deal. He died of cirrhosis of the liver two years later.
Your friend is a severe alcoholic, and that much beer will indeed destroy his liver. Perhaps you can suggest to him that he have some liver function tests done and to honestly tell his doctor how much he drinks.
There is a medical condition called nonessential tremors. I have this condition and normally alcohol does not affect it. My doctor has prescribed propanolol for it and this medication works pretty well for it.