OK, let me ameliorate my position; TM's are generally fine with green gas, and whilst they will not last forever, higher power gasses will degrade their lifespan. In all my years, I've not had first hand experience of slides flying off, though I've heard of it happening. And it sounds like this is something you've come across. I see this being a rare occurrence.
I roughly counted how many rounds I fired yesterday, it was over 500 and that was fairly average for me.
I think my point is that I think the fear that if you put green gas in your TM the slide will end up in orbit is overblown.
I still think OP's pistol was defective or damaged.