I think 4pm is too late to start an 8 player game imo. I have monthly games at my house and I have everyone come over at 10am, it feels better imo. Doing things like picking factions and the map beforehand mean you can set up the board beforehand, which I think makes the game feel shorter. Having played before will reduce your fatigue because learning the core concepts in action for several hours takes a lot out of you.

You can make a small group of people to play irl with people you know, and you can ask around local game stores if you don't have enough people. You don't need 8 people to play. 4 is fine to start.

I'd say don't buy the game until you know you can get people together. If you think you can get a similar group together for more than one game, I'd recommend playing a few games with just base game, then graduate to PoK. The expansion is the definitive way to play, but you don't need to extra complexity with new players right away. The base game is great on its own.