Anecdote here. I have existential anxiety too. I have the same fear of shrooms as you.

Salvia Divinorum "salva" when smoked has historically provided me with relief - it's great for someone who wants to stay in control because the high from it only lasts a few seconds (when smoked). If you don't like it, it will be over really quickly. A single session with it should set you right for a few months. Also, unlike most popular substances it is an "upper" - making you excited and happy instead of chilled.

Marijuana has the same effect as alchohol, during a high I'm typically free from ego (sometimes it extends to the next day). Good chronic provides a very powerful experience that I can only describe as the opposite of existential anxiety: I've had moments where I've found my temporary nature beautiful. If you haven't tried chronic before treat it with respect, take 1 hit and don't be impatient for the high. It's safer than alchohol so you might try that instead.

Although I'm really considering doing shrooms once after so many have said that they have helped.