1. So, is Glenn's suggestion that "they just didn't say 思う at the end" correct? Is it valid to leave off 思う and just have it assumed?
2. Hmm. I did wonder, actually, about the purpose of に when I was originally trying to understand the sentence, but I still have little feel for this は/には distinction. What pattern is に part of? I mean, does it go with 分からない, or is ことに a unit, for example? Could you give any other simple sentences that illustrate this, to help me understand the pattern?
4. Oh, gosh, you are right, it's 事. (Must get those stronger glasses!)