When will Darcy have a chance to 'win her over'? After the marriage he is proposing? Then it will not hold that this plan helped raise his confidence in a positive response to that idea.

Elizabeth has long had Darcy's acquaintance, and once (that I recall) started a conversation with him (Ch. 6: "Did not you think, Mr. Darcy, that I expressed myself uncommonly well just now...[]"). She need not cease to be a lady by smiling when a gentlemen enters a room, or beginning a topic with him, or by conversing with 'spirit and flow' - all of which I can imagine she DOES do with Colonel Fitzwilliam.

I think I can see your take on this episode in individual pieces, but when you put them together, you seem to be saying (please, correct me if I mistake you) that sometimes he thinks she is interested-but-demure, and sometimes that she will have to accept him, despite having no current affection for him.

I hope Darcy is not exploiting a societal trap - I hope he sincerely believes (in pride and arrogance, 'tis true!) that Elizabeth LIKES him. Then all of his attitudes come from blindness to her nuances in pursuit of his main goal.