0.01BTC minimum bid is too high. It should be 0.002BTC
What happens if somebody bids 100BTC with a Win Multiplier 66000x and wins - HOW DO YOU PAY HIM 6.6Million BTC???
Max bet should be something like this:
60%+ win chance: 100BTC
30-60% win change: 50BTC
10-30% win change: 10BTC
5-10% win change: 5BTC
2-5% win change: 2BTC
1% win change: 1BTC
and so on!
If you have 50BTC then maximum possible win should be BET AMOUNT+25BTC.