1. On the risk free debt, the cost of RFR will be close to Treasury yields, which is much lower than the expected return of 18% for the investment. Since there are 100 investment opportunities, the probability of loss can be diversified to a very small number. So we should borrow as much as possible to invest in this game.
2. On the confidence level issue, I mean we can use measures such as value at risk (VAR) to define risk, since there is no availabe data to caluculate standard deviation. By convention, we can use 95% or 99% confidence level to calculate VAR.