My worst moment is when I saw betking.io site how it is moving own faucet from site but I was invested about 0.3 btc to make wagered to make money from faucet and bring high rollers with faucet earnings when I advertise but Dean admin destroyed my plan and I was not able to do that so now I dont use betking.io and I will never use it anymore because of that and they also have slots which are provably unfair I know that because Dean admin told us that in chat so I dont like them better dont join there be like me use only faucet on gambling sites and play poker freerolls and get money without any risk 
Faucet amounts are just good for trying out the game but we cant guarantee to make money with it unless if we are lucky on that day,poker roll would do but it would need for you to play smartly.I dont see any issues regarding betking on the past but as you stated seems like they do really have a problem regarding on provably fair system. Worst moment on gambling when i lost 2 btc on playing dice and bustabit.