Just for reference, I intended for the poison to be added AFTER the attacking phase and HP reduction, like it does with thorn carapace. I'm not sure if it makes more/less sense but that's how I imagined it. Below is a nifty table to demonstrate.
Of course, healing can prolong its life indefinitely so go do that for the win. And the upped will be different yet again (Plus 2 turns if you use ability).
So the Attack probably is a bit steep and should be around 4/5? Lowered, specially since you can spread some CC around.
And thanks Odin for the art, I'll update it I change the stats (which I probably will)