You raise some interesting points. It's rather curious that the episode posits that your messing with time created the tornado in the first place and then tells you to mess with time yet again in order to make it go away. I can get where they wanted to go with Chloe because of Doctor Who; you know, fixed point in time and all that jazz. One could then argue that trying to change a fixed point in time is what creates the tornado rather than Max messing with time in general (although the moral is usually that no matter what you do you can't change a fixed point in time; there are no tornadoes involved). However, I don't recall Episode 5 ever making this argument. Worse, if you choose to save Chloe, the tornado hits and you're both alive. Does that mean you can change a fixed point in time but at a cost?

As for the "what's the point if everything is undone?" question. I get it, I share that frustration. I'm guessing the point is that you, Max, got to spend a few days with your best friend, who you hadn't seen for years. It sucks that only you'll know that, that you can't share it with anyone else.

It's kinda ironic, when you think about it. Evil Max berates you for going to extreme lengths to save Chloe but this all started because you tried to save some girl you didn't know from getting shot. Plus, it's not like this thing came with a manual.