This is an old thread, but I think #2 and #4 suggest there may be a BE/AE usage difference. A bit hard to explain, but I don't think "humour someone would be synonymous with "do a (
reasonable) favour" in BE. The point of "...humour..." is that the wishes of the "humored" are unreasonable/crazy etc.
Here's what Oxford online e.g. has:
verb [with object]
More example sentences
I had always figured he humored me while I chattered away so he could take some more pictures.
I can't really understand the distinct aversion felt by the three persons who humored me by coming along.
But the old man seemed to have made up his mind, and so, to humor him, he did as he wished.