Comma usage: "In July of 2012 ..." or "In July of 2012, ..."

The sentence is correct with or without the comma. But the comma introduces a break/pause, which can be helpful in a longer sentence, and personally I would include it.

As regards formatting of the date, British usage used to be to separate month & year with a comma, but more recent usage omits the comma. (I can't speak for US usage, although I suspect that the comma is more likely to be included.)

In any event, for both questions, it is primarily a matter of style: there is no right or wrong way for either point.

In July of 2012 can be seen as a weak interruption to the sentence, and a comma after 2012 can be justified for that reason.

There’s no reason to put a comma after August. In fact, in British English, the date would probably as 15 August 2012.