OD is the least likely way to die.
I think Xanax would be the most likely to do the deed but it's still like 5% chance of actually dying. The problem with OD is that the toxicity isn't certain (LD50 is what it takes to kill 50% of MICE), and the chances of puking and this losing the toxins are high.
Any OD or attempt at CTB are more certain with an antiametic (something that reduces nausea and vomiting), but the chances still aren't good.
I think I'm that realm Phenobarbital, Cyanide, and Sodium Nitrate are the most likely - none of which you've mentioned... and I've known enough people who tried to CTB with benzoes to know that it's a pretty unreliable way.
Sorry you're struggling. Sorry I didn't have any good news for you - you're more likely to get sick than die.