1. If Itachi was Jiraiya's secret spy he would have known more about Pain, or at least that Konan was in Akatsuki. There is little chance that he was Jiraiya's spy from the lack of information Jiraiya had.
2. Itachi was a criminal when he killed his clan, there is no grey area between 'actual' criminal and 'official' criminal. He could have not killed his clan and never been a criminal. If you are meaning when did he do his first criminal act on his own volition with Akatsuki, then the answer is never.
3. Itachi's 'double agent' nature was the ultimatum give to Akatsuki that they could not attack Konoha without Itachi uncovering them. He may have been gathering info/protecting Konoha, but we have no knowledge of that information getting back to Danzo or anyone, otherwise Konoha would have been far safer because Itachi would have said something like "I am the only reason they aren't attacking Konoha"
