So, I'm a student in the Veterinary Technology field, but when I finish my Bachelor's degree, I plan to switch to the Medical field, and pursue an M.D. As it stands right now, I have a year's worth of introductory medicine, and more thirst for knowledge than I've had studying any other field, ever... Anywho:

Question One: Epinephrine is commonly administered to patients for allergic reactions. My understanding of anaphylaxis is as follows: basophils flood the IV space, dumping histamine into the bloodstream. The large amounts of histamine result in extreme vasodilation, resulting in fluid flooding the interstitial space, resulting in swelling, et cetera. In the cases for which airways become compromised, Epi-Pens only deliver Epinephrine, right? But, all I know about Epi is that it's a neurotransmitter that stimulates the sympathetic nervous system, resulting in vasoconstriction, which would prevent anaphylaxis from worsening, but... In what manner does it reduce the swelling/edema, and save lives?

Question Two: Daily intake of water. Within context of my studying, I've learned that daily intake of fluids should be 1mL of water per kCal of energy, assuming normal losses (may be derping this up a little). Translating this into the "2,000 Calorie Diet™" that's the baseline of everything ever, this roughly equates 2 liters of water, which is, more or less, eight cups; which totally makes sense, right? But I keep seeing this bit of information thrown around that it's totally okay to drink a lot less water, and "you get most of your fluid intake from the food you eat." How does this particular bit of information play into real life?

Bonus Question: If I, a 110kg white male, were to increase my water intake to three liters a day, what would the potential side-effects be? (I ask this, as I've read in a few unreliable sources that this can help with weight loss, as well as increasing levels of hydration; I'm on the poor-person's high-sodium diet, so I worry about such things)