“Bingley had never met with pleasanter people or prettier girls in his life; everybody had been most kind and attentive to him; there had been no formality, no stiffness; he had soon felt acquainted with all the room; and as to Miss Bennet, he could not conceive an angel more beautiful.” (Chapter 4)

One of the reasons I accepted the definition given by Margaret S is that it is the only definition listed for “awful” in my copy of *Samuel Johnson’s Dictionary, A modern Selection which is based on Samuel Johnson’s Dictionary originally published in 1755 which I have heard tell is the dictionary JA used. I will admit to the possibility that I am misguided but if not then it is much less likely JA was using a definition not in use at the time—no slur intended upon her lovely self. :D

A second reason is I agree the insult implied by the use of the modern definition of awful equals dreadful seems out of character for Bingley. If you consider that he is poking fun at Darcy’s serious awe-inspiring demeanor instead of saying his friend is dreadful then the insult is gentled IMO not to niceness but to a more Bingley-like joke about his friend. ;D

He began to wish to know more of her, and as a step towards conversing with her himself, attended to her conversation with others. His doing so drew her notice. It was at Sir William Lucas's, where a large party were assembled. (Chapter 6)

Caroline defends Darcy from anyone and everything so I think the suggestion that Darcy is uncongenial to the extent of obnoxiousness when bored (I like your description) is enough to raise her hackles and attack. Lizzy thought Darcy listened in on her conservation with Col Forester in Chapter 6 because he wished to criticize her—“He has a very satirical eye…” so I cannot be sure Lizzy is correct that Darcy is angry when he smiles. Perhaps Darcy smiles because he is amused by Bingley’s way of ending the discussion. ;D