As someone going through it from your son's side, I can tell you a few things. You're blaming yourself and putting too much pressure on yourself.

The teacher part: my mom's a teacher too at a pretty prestigious school. She has no idea. Even if she did, she couldn't have done much.

You did all you could have possibly do. Absolutely all you could do. You have nothing you can blame yourself for. Your brain is now bombarding you "what if I did this? What if I did that? What if blablabla". Odds are it wouldn't have made any change.

Faking it until you act your plan out is easy. I've been pretending for several years(9) and no one can tell, except for a few really bad moments. If I decide to do it one day, there isn't anything anyone can do to stop me. Some people are just too far gone. The pain is too unbearable and there's nothing anyone can do.

I'm sorry for your loss. Please try to heal! Take it one day at a time...