More specifically, drinking distilled water is bad because it leaches minerals from your system. It's better than nothing, but if you're in a tight spot you could mix a sports drink concentrate or some kind of electrolyte powder into it. Remember the rule of threes: three minutes without air...
I think the pacing is weird because there's a lot of stuff happening everywhere when for most of the manga, it was focused pretty much only on Itami and his immediate circle with the odd chapter or end of volume bonus to develop the rest of the cast and setting. Because of how much is happening...
The enumeration is off compared to the official releases (When Johnny Comes Marching Home is 79 in the tanks), but there are ten chapters that haven't been translated.