+0
Clark: Isn't there a limit
to how tight a shirt can be to meet dress code?
He implies it's too tight
even according to dress code?

Lois: Really? Even you? Are you mocking me too?

Clark: Well...
Lois: I never made it to Mexico.
Clark: Right, can this wait until after your post-lunch, Before lunch?

predinner, after-coffee (coffee break?) snack break?
+0
"Post" means "after." "Predinner" means before dinner.

He's just making fun of all her breaks, referring to some of them by way of describing another one.

"after-coffee" would be after the coffee break. All of these qualifiers refer to the "snack break" at the end of the sentence.

Your earlier suggestions are both correct.
Comments  
Thanks, Avangi!