1) I don't actually know how this system works in any depth. I'm returning to VP after about a year of inactivity with it. I don't know how a city that has plenty of food and production can be distressed. It's not like I'm starving it. And it's on such a powerful scale. Distress here, distress there, distress everywhere. Why? I don't have the answers, so I don't know how to fight it. It feels like all I can do is just build buildings that give -1 distress, making barracks a new high priority building. Is this based on some global average? Empire average? And why is it so high despite working so many high yield tiles? Not only does assigning a specialist add urbanization unhappiness, does this not also make your city "more distressed"? It's so punishing.
You don't need to know the depths. You are mostly suffering from needs, I guess, otherwise you'd be complaining about war weariness. Your citizens require an amount of yields each one. They base their demand on the world average yield efficiency. If the world's median city is producing 10 gold per person, in your city they don't want to receive less. But there are also some modifiers: each city you control adds up to the modifier, each technology you gain also increases what your citizens aspire to get. If you hover over the unhappiness tooltip in the city view screen, you'll see a summary of the modifiers: technology, empire size, and any buffs you gain from buildings. It also says the estimated happiness change upon growth.
If you are struggling too much about needs, it's because you either expanded too fast or grew your cities too big. Once you start having troubles, control these factors. You can have more cities with fewer population, or fewer cities with larger population, depending on terrain and your choices, but you can't have it all. As you build your infrastructure up, you'll be able to expand further or grow bigger.
2) More than ever, it feels like you have no choice on what early buildings to build. The answer is just to build them all (just to get your city to shut up about its needs... only for another to take its place). Why should I be building walls in a city that's on the inside of my empire with no risk of attack? Why should I be building barracks when I don't wish to train a specialized military? I do have the answers to these questions, but it just feels like even buildings you would selectively choose not to build, you now have to.
If you have overexpanded, then yes, you need barracks and walls ASAP, and any building that directly contributes to your deficitary yields (arenas make barracks produce extra hammers, for example). But you could have not overexpanded and you would have a bigger flexibility over what to build now.
Also, don't disregard what you gain from the terrain. If you manage to form a farm triangle adjacent to a river, some of these tiles are going to yield 4 or 5 food with just one worker. You don't need to work all these farms, but you want your workers to be working on very efficient tiles. A hill with a mine and a forge is yielding 5 production per worker too. So, the direct way to combat distress is to work on mined hills with the forge and on some farm clusters near rivers. If your city is going to grow and there's no good tiles available and you don't have spare happiness to use specialists just don't grow, choose low food tiles (more mines, less farms) or directly click on 'avoid growth' button.
Anyways, if you only care about distress, you are going to miss technologies and policies coming at the right time, so it's not wrong to endure unhappiness for a while if that gives you a policy in time.
