City: Fred. He’s a good neighbour who gives you goodies and a really useful duffel bag (which allows you to carry extra items), and leaves you chili in his house.
Suburbs: Sean isn’t very popular (not a lot of people like him), but his house has some really cool items. And the suburbs don’t suffer a blackout, so you don’t lose half of your food on the third day.
Countryside: there’s a well, so you won’t run out of water.
The first one to appear is Lopez, around 10:00AM. Then Tommy, between 12:00PM and 2:00PM (here I’m not 100% sure, but you have until 1:30PM at least), and lastly, Dante, between 2:00PM and 3:00PM.
Once you know how much each event takes, you can arrange what suits you best. For example, if the first thing you do after breakfast is repairing your home, which takes 45 or so, then do another activity that takes 15 minutes (changing clothes, filling bottles with water, etc.), you will unlock Lopez’s event at 10:00AM sharp.
Each outing (for scavenging) takes about 1 hour, except the three-story house, that one needs a lot of time (like 3 hours!). Depending on your cooking level, having a meal can vary to 15 min, 30 or 45; helping Lopez, Tommy or Dante also take time, so take into account how much each event lasts and start planning what suits your tastes better.
It’s definitely possible to scavenge all houses and save everyone
Mmm… I’m tempted to say the scientist one, because the cure is vital, but it won’t be of much good if you die halfway making it. So… the soldier route, because once you reach a military base (was the name Lancelot? I dont’ remember much…), which will be a true Safe Haven, you can start investigating the virus if you have the skills, or look for someone who has them. And if you don’t manage to find/develop the cure, at least you will be safe from the zombies.