I don't really think about what's 'age appropriate' for my audience because I think they can handle quite a bit, but I do try to think about what's honest and true to my characters who have grown up in situations where they've been taught to handle these things very carefully and that they're very powerful.
All I try to do is as earnestly and as acutely as I can, conceive a character and try to portray this character just honestly. If the humor is within the absurdity and the awfulness of situations, then let it be seen that way.
You have to respect who the character is. It has its own internal truth, and you can't betray that. And if you don't betray that, it will not betray you.
I want to remove the curtain of pretence from all of my characters.
The only rule I have in how I let characters tell stories is that they must always tell the reader their version of the truth. No one likes being outright lied to, even in fiction.
It's much simpler to be tortured on camera or to be filmed losing your mind. Whereas a script that has characters who are honest, witty and genuine is often much harder to act.
You play the honesty of the characters and show a side of them that people can relate to and want to get to know.
Trust your actors. That's why I work with the same actors time and time again. I encourage them to change the dialogue to achieve one thing: keep the characters honest.