I do agree with most of your points. But I cannot see Mr. Knightley scowling and disappointed because Emma ONLY acted the hostess, without any friendly feelings involved, and imagine that he is not placing a high importance on Emma becoming intimate with Miss Fairfax. He probably has good goals in mind while doing this: I imagine he thinks Emma will benefit from the interaction as much as Jane Fairfax, and it will distance Emma from the friendship with Harriet, which he deems unfortunate for both.

However, I see Emma's good intentions for Harriet through the twinned lens of self-conceit and probable ill results, and, using THOSE criteria, Mr. Knightley's intent to use his influence with Emma to force a friendship (which seems obvious to me), is impudent and short-sighted.