I think if you think you have a legitimate claim against this site then post it in the scam accusation section. OP offered you a 1btc bounty to prove your claim. Take him up on the offer or move on.
What you have posted can be photoshopped so its not real proof to me. Feels like an extortion attempt. If he wanted to screw you hed have screwed you on all your bets right? Looks like you or someone was paid .1 and .08 according to a post prior to this 1.
Yes thats a nice idea, if you are so sure the OP scammed you why don't open a scam accusation thread and mention there that OP telled you that if you prove he is cheating, then he will give you 1 BTC, but proofs on video are more trustable than proofs of images, which can be manipulated more easily. With video proof you can even speak while recording and thats more plausible. I suggest to you , you do so, I would do so for 1 BTC if I was sure and had all evidences the OP was scamming me.