I think the 12g of N you have will do the job no matter your fears or how much you think your CNS is messed up. Ultimately though, you must be comfortable and at peace with your decision.
Although the net effect is the same (shutting down your brain), opiates/opioids have a very different mechanism of action than barbiturates. When combined, they have synergistic effects.
It's complicated. 'normal' people would die from 12 gr of N ... And the literature states that the lethal doses varies from 2-10 gr ...
Opiates: I think I did read about two mechanisms in the literature, it has been a while.
1) certain receptors affect voluntary breathing. Presumably, when unconscious this could definitely have an effect. That theory is new to me.
2) opiates act on the brain stem, directly depressing respiration. This would be an involuntary mechanism.
Both N and opiates kill by acting on the brain stem. In that sense, different receptors but same mechanism of action.
I did experiment with something recently, and that did cast some doubt.
I'd dread surviving this and being at the mercy of the medical gods for the rest of my 'life'. Never underestimate the ability of the human body to survive. I'm not fine and I really don't want it to be much worse.
I know I need to read up on the theory.
It;s a mindfuck that N+opiate is peaceful but not 100 % certain. Sodium azide offers 100 % certainty but I'd be tortured to death for a few hours ... What a choice ...
I could do it all without fear but he thought of waking up ... or being confined in a paralyzed body. Oh, and if you are afraid: N helps with that ...