1. It's all up to you, You can either split or place the maximum order of allowed coins. But if you do the latter, you could easily make the price of the coin dump quicker. Other traders might also end up panic selling.
Why don't you place part of the amount of coins you have as bid orders, you can also be part of those creating the liquidity for the coin
as people keep slowly but surely filling up your orders with time.
2. Most exchanges do, but like I said, a huge dump like that can be reflected on the volume and candlestick and this can trigger other traders to also panic sell and eventually the token/coin would be worthless
3. Other trading pairs will also drop in price. There are traders who do arbitrage kind of trading. They will be looking for those price differences and try to make profit out of them so within a few minutes, the prices of all the trading pairs will drop to the same level.
4. Place part of the coins on the other part of the order book (bid orders) as I said in 1. Be patient. If you sell all the coins at once, you might crash the price of the coin, and you could also lose out