Have half of BTC at hand. Want to find a way for better investment rotation to be done. So far invented such a scheme. The whole amount to be exchanged for any local currency. Surplus since last investment to be converted back to BTC. Remaining - initial investment - to be spent on daily needs. Converted BTC to be put back into wallet. Two points of interest here.
First: Does this way of turnover looks reasonable at all?
Second: How to make sure I use "clean" BTC from source of exchange?
I didn't get what you are trying to say correctly. Why would you convert all your bitcoin to any fiat in the first place. Why don't you only convert the ones that you will be needing for your daily needs
to your local fiat and leave the rest in bitcoin. There is nothing like clean bitcoin or tainted one. Government is only using those words to make it look scary. Bitcoin is bitcoin.