I recommend you to set Trading Limit to something higher than the minimum. For example, if the minimum amount to trade is 0.005, I would set trading limit at least to 0.008 or 0.01 and min_vol_to_trade to something like 0.007
Some exchanges like Binance leave dust and it's something "normal". What I do is, from time to time, to use Binance tool to convert all the dust to BNB and then convert BNB back to BTC.
Also it's important to note that the lower your trading_limit is, the higher the impact of the dust will be.