2. When forced to buy two seats, insist on using the seat right next to the other passenger in your row. You have paid for both seats and you should use them. Spread out. I don't think anyone would have to INSIST. That's the plan. You get two seats, you use two seats.
I was thinking more of the person next to the POS (Person of Size) complaining and the FA asking the POS to move to the other seat.