1) hard to say. But it feels like they have put in a number of ideas, above +
- armor stand was heavily asked for
- unarmed weapon was asked for
- mounts were asked for
and so on.

2) Yes, I bet they play. And I feel it is a key part of success: if you don't play it, you run out of ideas I think. But playing it, you find something you don't like and think "I wish we had a whatever" or "this interface is terrible" or "hey, that is a bug" etc.

3) I think unity has a bad rap. It may not be the fastest, but this game shouldn't be the most demanding either. The performance could be just untweaked code. The rule is get it working and done, profile it, find the bottlenecks, attack those. They are on step 1.

4) hmm. I think it was when I got my first stonecutter and not long after a brutal raid .. I realized there was much more to building and that unlike many games, your home actually matters instead of just being a cosmetic playground.