Put a vertical scratching post right next to the couch, like literally leaning against it, and rub some catnip or cat spray on the scratcher to get his attention over there. At the same time, remove the blanket because that's really the opposite of what you want - it makes it more fun to scratch. If he keeps going for the couch, use double-sided tape (the sticky kind) on the arms and back, cats hate that sticky feeling. A new scratching post definitely helps, but the real secret is making it clear what the "right" place to scratch is by offering better options than the couch.