I'm not too sure about your #4, but #2 definitely cannot be counted upon to be true.

In Chapter 92, in a conversation between McG and LV:

“Are you mad? You think that Mr. Potter could—this is ridiculous. Mr. Potter cannot possibly—” A wordless image crossed her mind of a patch of glass on a steel ball. “—Mr. Potter would not do such a thing!”

It has been pointed out that if LV discarded treating this as a game, which does appear to be the case, then he may well have been using Legilimency on McG, in which case he would know of it, at least.

Which isn't to say that we couldn't use it to bargain for the lives of others, or whatnot. But you can't trust that it's still unknown to LV.

Furthermore, have we seen Harry transfigure the air? I remember him speculating that he could, trying, and failing. I don't remember him succeeding at a different time.