The Blue Ocean Institute has devised a simple way to help answer the first three questions easily enough with their cool service called FishPhone.
1. Text to 30466 FISH + the name of your potential dinner victim.
2. They'll text you back an environmental thumbs up or down.
For example, I texted them for Artic Char, and their cheerful reply was,"Farmed Artic Char: very few environmental concerns; most char are farmed in inland facilities that cause little pollution."
It won't give you PhD-level insight into the issue, but it's one step closer to gaining peace of mind at the fish market or while perusing the specials menu.