2) The bids and asks are real - you can anytime make a sharp move and buy/sell into the asks/bids and then even the most fake wall becomes a real wall. Therefore holding fake orders is risky business as they get sometimes filled.
Fake orders have the similar risk profile as shorting or leverage - most often even if your "fake" wall gets bought, you can buy back cheaper as the price will fall down afterwards and you have got 10% or whatever premium for your coins, allowing you to buy back lower. But there is the chance that it happens as part of a level-up, in which case you lose out of these coins.
So, "fake" walls can become real walls if the strategy is formulated as:
"I will buy it back if I get at least 10% cheaper, if not, it will be a permanent partial cash out of my long term position."
This strategy gives you peace of mind when operating large fake walls.
I wonder why I know it