First: Does this way of turnover looks reasonable at all?
Reasonable, as long as you enter and exit at the right time. It's faster to make a lot of money using this strategy compared to lump sum or DCA. But I don't have balls to flip my money, so I choose to invest with DCA strategy.
Second: How to make sure I use "clean" BTC from source of exchange?
Make sure:
1. Never use instant exchange.
2. Whenever anyone want to send coins to you, ask them send them directly from centralized exchanges.
3. Never do P2P.