I also think, that, strictly pharmacologically, the lack of sleep doesn't affect the pharmakodynamics of poison.
However if you have actually been sleeping 3 hours a day for a week and you say "my brain ain't working fine" sounds like you might be manic or you have taken some substance that is really affecting the way you think.
IMO it seems unwise to go for CTB under conditions that suggest that your clarity of thought is impaired. I myself would or will CTB only with clarity of thought, as a rational decision à la Swiss or Dutch.
Tbh I have read both that SN works and that it doesn't, one case has been reversed with 97.5% meth-Hb in blood. One of the warning labels on lab-grade SN is "oxidizing agent". I want to read more about it, because if it burns my oesophagus and stomach idk. But the "oxidizing agent" warning is found on many substances with varying effects. So who knows.