Playing it must be the biggest help. It gives you a context to understand the rules when you re-read them. Folk find we'd made a few little mistakes on our first play through.
1: Yeah activating a survivor just means to use it, in having it's turn. It helps to back up the notion that ones that survivor's turn is done, it's done, so you can't do a couple of actions on it, do a couple on another survivor then go back to the first one.
An extra activation does mean a whole extra turn. That can be kind of awesome when it's a survivor that gets an extra activation from the Zombie Link skill. If a zombie type gets an extra activation that whole type gets another go immediately. That can be a game over situation. We really learn to be afraid of runners especially.
It's made us mindful of how we spawn in buildings. If you start from the door you've just opened and the zone at the back gives the chaps in front an extra activation, that can be a grim situation, so we spawn the zones starting at the back instead because in the zones in the front give them an extra activation it's less immediately painful.
2: That first player token denotes which player goes first, that turn. Because in the end phase the first player token is passed on, so a different person goes first each turn. It's a good thing it passes on, because too often the last person to go has nothing left to fight and lag behind in exp. It also throws in an interesting dynamic, in planning for the next turn with the knowledge of who will going first and last.
3: I think there's a cheat sheet on the back of the books listing the phases of a turn. Survivors phase, zombies phase, spawning, end phase. It's a bit of space in the turn order to do admin, remove noise tokens if you use them and any other turn based effects, pass on the first player token, take a breath.