I agree that time three is correct. I don't think you need to resort to em dash in the other two instances; a comma would suffice since what comes after each looks like a modifying clause for the previous statement. Not that I think an em would be incorrect, just that normally when I use them it's to really pause and make an aside. I think the author's intent is just to modify the statement, in which case I would always go comma.
So, my understanding is that either an em dash or comma would be correct in these instances. I could be wrong. I voted for el dash because I feel like the way the author is abusing the semicolon indicates they're trying to create a break but then add on/move on. However, esp in the first, I see how you could argue a comma would be more, or at least as, appropriate. I've tended to be an em-dash happy writer in the past, myself, which would also explain why I chose that option.