The 6,75% are on a per year base and of course, if you withdraw after one month, you will get a 1/12 of it. This is the fixed model, with the micro-loans the ROI is much higher (but also the risk).

Not at all, I have a lot. I am just skeptic about the overall return (in case you don´t have exactly those cryptos and you would buy them just for the staking profits).