Standard deviation is not cute. It's a real thing.

Whether or not the downside risk is immense, is for the original poster to decide.

I don't know what n0 is, nor do I want to play this game. I came up with an aggressive bet ramp that allows the original poster to play for a small profit, although, as you pointed out, with a gigantic standard deviation.

70 rounds per hours is very realistic for a live casino. The original poster is talking about an online casino. I've never played online, but I imagine rounds per hour would be about the same, or even higher.