1) The folders that need to be replaced or added are listed, so you can just follow those. Everything else is likely unchanged.
3) This sounds like something that could be done with the watcher entity. Basically, the spawners you get close to are deactivated by the watcher, while the further ones are activated.
4) What kind of bonuses? Like gadgets in SS4? The Serious Bomb?
5) Yes, that is exactly what it was originally built for. It's limited, in that you will have to do a lot with triggers, but a lot is doable.
6) There is only one option for the enemy projectile. It uses the same entity that Mordecai uses and that one has only one kind of look. But if I ever figure out how to add more, I might do it.
7) Fall damage is all kinds of weird. If I remember correctly, the only customizable thing about it is, having it turned off for certain polygon types (standard no impact, for example).
8) That kind of information is contained within the sector type. It's probably possible to have it be customizable, but that would require programming a whole new option into an intrinsic property, which would probably break a lot of things in the process.
3) Yes, that sounds good. But I checked what can be implemented using teleporter spawners, so as not to take into account extra enemies for statistics that will not spawn. The screenshot above shows approximately how it was intended by me.