The spent barley makes a fine pig food. Make it a portion of their ration, not the whole thing. If their poop starts looking like the incoming grain then back off on it. I would also suggest feeding veggies and pasture with it. Ease them into it. See how they do. We feed some, I would love to have more.
What animals eat effects the flavor of their meat. The flavors get stored in the fat primarily. Barley is fairly neutral as flavors go.
I suspect you could. I have never tried feeding it. They say liquor is quicker although candy is dandy.
This is an interesting concept. It would be interesting since many things are flavored or marinated in something with a beer, or some type of liquor base. This would get a jump on that. Maybe a new market?