are the "rewards" generated or used from the entry fees? wanted to check if it will affect game balance in any way 

Generated. The only one that will affect the game's balance is the blackjack function because for the raffle, you need a minimum amount of poeple to join so that one will technically be used from entry fee.

I'm guessing the black jack works similar to how the gamble in the bandit zone works right? coz i think that is also generated but they can get to lose their "bet"

yup, but I think my plugin will be useless next Rust Patch as they're introducing slots.