This is a very interesting, well-written post, which leaves me a little surprised you missed the whole point of "The Gambler". It's not the James Caan character doesn't know WHEN to stop. It's that he only feels alive when he DOESN'T stop. Which is why even when he "wins" near the end (in the sense he's now even and won't be killed), he immediately puts himself in a different dangerous situation. That rush is what he craves, that's the addiction.

And it seems the author was craving that feeling in real life as well, as you saw for yourself.