My Chemical Romance - Na Na Na (Na Na Na Na Na Na Na Na Na) Lyrics Meaning

Your interpretations are all good, but I would like to tie up some loose ends.

"The future is bullet-proof.
The aftermath is secondary."

These lines indicate the nonchalance for the future some people have.
"The future is bullet-proof" (unchangeable)
"The aftermath is secondary."(The outcomes of your actions are insignificant)

"Drugs, gimme drugs, gimme drugs
I don't need it, but I'll sell what you got
Take the cash and I'll keep it”

People don't care for the outcomes of their actions; they only care for their own needs (money, comfort etc...)

"Fuck like a Kennedy"

This suggests at how people take pride in things they shouldn't.

"Let's blow an artery
Eat plastic surgery
Keep your apology
Give us more detonation"

"Let's blow an artery"
As -DirtyDanTheMAndrews said, it refers to our fast-food culture

"Eat plastic surgery"
People want to eat unhealthy foods yet keep thin.

"Keep your apology"
Some people don't care about the consequences of their actions on others

"Give us more detonation"
Detonation refers to things that will cause harm to the person and others around him/her in the future.

"Everybody wants to change the world
Everybody wants to change the world
But no one,
No one wants to die
Wanna try, wanna try, wanna try
Wanna try, wanna try, oh
I'll be your detonator"

He is inviting people to help change the world and volunteering to “be your detonator". Be the person who lets the person "explode" feel the consequences.

"Make no apology
It's death or victory
On my authority
Crash and burn"

It refers to people’s 'do or die' attitude, expecting others to give it all for their leaders cause, hence "On my authority Crash and burn"

"Drop like a bulletshell
Dress like a sleeper cell
I'd rather go to hell
Than be in purgatory"

"Dress like a sleeper cell"
People who want to fit in try their best, even though, deep down, they know they don't belong

"I'd rather go to hell
Than be in purgatory"

Purgatory is the place in the Middle ages where criminals, willingly or unwillingly, tortured themselves in the believe that they are atoning for their sins, and thereby increasing their change to go to heaven