1. It's not even a one move pwn you can easily defend it with basic methods learned in the zabuza arc about how water with chakra inside of it is heavier. Thus they would realize it's a jutsu. It's not space time, it has to flow into the person. Which you could then just use, iunno, a certain wind technique that forces air from the lungs, body water technique, a simple fire technique causing evaporation so that he loses control over the water. There's seriously numerous counters.
2. He used the technique on his own, not me. However, if someone wants to say what my technique can and can't do, then you can bet 'm going to be there to defend it before it turns into something worse. Like not being able to control the water at all or some crap. I'm not gonna start letting my own jutsu fall victim to some argument.
3. The water jutsu states, the user creates water from the moisture in the air within mid range, they can then control that water. Breathing in air, air has moisture, however they'd need to take control of the moisture before it enters the body. Not sure how that's unrealistic all it takes is paying attention to the usage in order to defend.