I'm trying to work out a personal policy to determine when a ponzi should be flagged as a ponzi - so that everyone is treated equally.
I think one of the guys you're arguing with misinterpreted "personal" here. You mean personal to you, not to the person running the Ponzi game.
My personal policy is that a Ponzi is a scam if it is deceptive, and not if it isn't.
If you run a Ponzi and say "we will double your deposit in 24 hours for as long as we can; deposits will be doubled in the order they are received; if we ever go 7 whole days without being able to afford to double a deposit, we will shut down and keep what's left over" then that's OK.
If you run exactly the same Ponzi but describe it as "we guarantee to double your deposit in 24 hours; we can do this because we whore out our grandmother; and she's really hot, man" then that's not OK.
The 2nd kind is by far the more common, with the owner swearing blind that he has some magical way of doubling any amount of money, and look, here's proof because we just doubled a deposit of 0.001 BTC...
Edit: It appears the OP has increased the minimum playing amount by tenfold. 
The way he has it set up makes it best for the player to split his bets up as small as possible, to maximise the chance that at least some of them will be successful. He should change that, and in doing so remove the incentive for people to make lots of tiny bets.