Okay, I've watched it. First, congrats on the win
I actually don't think this guy is a map hacker. On the oracle harass deflections, he had his army camped in his mineral line long before the oracle was out on the map. A big indicator to me is that on the first harass, he kept one stalker at his ramp, even though you didn't have any ground forces moving out. It would have been more optimal to move all the stalkers to the mineral line for defense.
The fishy stuff would be (to me) when he moved his army down his ramp right before your first attack (he still left 2 stalkers in his mineral line still, indicating that it's probably a playstyle thing) and then of course the observer vs the DTs. I don't have an explanation for either of these events, but what gets me about the observer (and the whole game) is that he never moused over unexplored area to check stuff. Never looked at your base to see what tech you were going, never saw the DTs on his screen before they hit his base (so how could he have known they were DTs to build the observer?). I think it was just good luck on his part.
Final note on the DT stuff, watch how he reacts AFTER he kills your DTs. He checks the main for DTs. If he had a maphack, he wouldn't have checked the main, he'd have known there were no DTs there.