1. Anyone else think that's not Kyubey's true form? We know he's got extra copies of his body, which implies that it's synthetic to start with. The form we see is just a little bit too cute to be a coincidence. It's exactly the kind of critter I'd choose to appeal to 13-year-old girls, Kyubey's target demographic.
2. It seems clear that Sayaka Miki was only chosen by Kyubey as a way to get closer to Madoka, his real target. She doesn't seem to have a tremendous amount of potential as a Puella Magi, and in the first repetitions of the timeline (when Madoka isn't very powerful herself), she doesn't become a Puella Magi at all. In the main timeline, after she becomes a Puella Magi her career consists of getting into trouble over and over again, at which point Kyubey inevitably turns to Madoka and suggests that she can help Sayaka by making a contract herself. Hmm..
3. It's impossible to tell how much Kyubey is manipulating things behind the scenes, but I don't think it's a coincidence that Madoka and her friends are continuously being imperiled. Kyubey loves the “hard sell” - making a deal when the other party doesn't have a choice, exemplified by the contract Mami has to make with him. Whenever trouble does erupt, Kyubey's first response is always to suggest that Madoka (and Sayaka, early on) make a contract with him. I don't know whether Kyubey is setting up the fights with witches (although the fight with Charlotte feels like a set-up to me), but he's definitely encouraging the girls, particularly Madoka, to put themselves in unnecessary danger by tagging along. Then he waits for a crisis and prest-o! Hard sell!