Yeah, I'm afraid you just sealed it for me as well, DavidB.  As your attorney, I advise you officially not to go down this road.  If you must, I agree that mescaline is likely your tamest alternative.

The existential crisis you've just described sounds EXACTLY like DMT.  In fact, there is nothing on Earth (that I'm aware of) which facilitates this exact experience like vaporized DMT.  It's not for you.  Trust me on this.  Heed the experienced posters above that are telling you more of the same, and save yourself from a world of hurt.  You don't want to face down these demons.