In the novel Col Brandon does not act like this and he does not seem angry until he confesses to Elinor. How do you think the countenance and behavior of S&S3’s Brandon compares to the Original?

I agree with you that Austen's Col. Brandon hides (or controls) his anger quite a bit better than S&S3's Brandon, and I also admit that asking Willoughby what his intentions are toward Marianne certainly isn't in the novel, and in fact makes Brandon appear more confrontational than he should.

However, it should be noted that Brandon in S&S3 has a fair opportunity to kill or seriously maim Willoughby in the duel, and he chooses to spare him. In the book, I have always assumed that Brandon fully intended to kill Willoughby if he could, and was only prevented from doing so due to the inaccuracy of Regency era pistols and the code of honor that would have to be obeyed during the duel. What I gather from the original S&S2 screenplay is that Emma Thompson probably had this exact same opinion about the duel, so the original intent for S&S2 must have been to have Brandon going into the duel with the intention to kill Willoughby, whereas S&S3 clearly indicates that Brandon only meant to humiliate him, and so had no intention of doing anything more than giving him a minor wound.