Can someone explain to me how the "1000% FREE BTC bonus" is calculated? I expected 0.0007 reward since 0.0000070*1000 = 0.0007 but instead I get around 0.00002000 or so.
It's times 10, not times 1000. Think of it like this.
100% is 100 out of 100 (one "whole") so naturally 1000% would just add another zero and thus become 10 "wholes".
The fact you get around 2000 satoshi is just your other Free BTC bonus added on top of that number.