I'm used Bittrex, I find a lot in Bittrex profits, exchanges are also easy and convenient, but Polo better because a large volume of transactions. The transaction fees at Polo and Bittrex equivalent.
# 3 has not thought out the optimal way
Although I cannot negate Bittrex is good exchange for earn profits recently, but if you want to ask me about exchange for day trade, I recommend you should trading on Poloniex exchange. Poloniex can gives you a chance margin trade and helps you take advantage all trend on the market.