Commas are not your problem.

"a great way to play off who he had been and whom he has become"

It is not a question of wanting.  The throne is mine.  Now bend the knee, or I will destroy you.

"And here’s the annual reminder that the main difference between David and I…"

Most of you pedants should consider yourselves lucky I don't hang you for treason.  Now bend the knee, or I will destroy you.

A comma should usually follow the participle "saying" when it precedes a quotation, but since you were not entering a narrative, it is not needed.  You have done well.  Now bend the knee, or I will destroy you.

You would do well to heed the advice of Maester Cappadocius.  Now take my course, then bend the knee or I will destroy you.
http://i47.tinypic.com/1emf…

You would do well to heed the advice of Maester Cappadocius.  Now take my course, then bend the knee or I will destroy you.
http://i47.tinypic.com/1emf…

He will take my course, then he will bend the knee, or I will destroy him.
http://i47.tinypic.com/1emf…

He will take my course, then he will bend the knee, or I will destroy him.
http://i47.tinypic.com/1emf…

You mean his pre-"ER" career, which included his role on the sitcom "E/R" in 1984-1985.  Punctuation is crucial.  Now bend the knee or I will destroy you.

You mean his pre-"ER" career, which included his role on the sitcom "E/R" in 1984-1985.  Punctuation is crucial.  Now bend the knee or I will destroy you.

@avclub-8e3b3550b00b4eae43a21cfb2eccf60d:disqus   Of course I am right.  You will attend my class, you will pass it, and you will bend the knee or I will destroy you.

@avclub-b7ee6f5f9aa5cd17ca1aea43ce848496:disqus "…whoever was blowing him at the time."  It's the subject of the clause, the entirety of which is the object of the infinitive "(to) blame".  Now bend the knee, or I will destroy you.

@avclub-fff4ac4c2f46e5cd75ec8b515c235031:disqus  "He didn't pursue…  he just admired her sharpness."  Achieve tense agreement, then bend the knee or I will destroy you.

"Who's allied with whom."  Object of preposition.  Now bend the knee or I'll destroy you.

"Shuddering as its tires melted."  No apostrophe.  Now bend the knee or I'll destroy you.

You are "loath" (no "e") even to post them, and you don't want to spoil the end totally (avoid split infinitives).  Now bend the knee, or I will destroy you.