We don't want to get into too much detail as we are aware of few competitors (though they don't offer their platforms to public but to selected clients instead) but we can tell you that your thinking is on the right track.
Historically we've been able to make up to 8 % profit a month. This is reasonable arbitrage profit - anyone claiming to make more is probably fraudulent, so beware.
I can't answer the pooling question but will tell you that we make sure it's 100% fair for all users.
