Are there limits to the number of points increasing/decreasing in a short span, ~2 seconds, of time? You might take drugs and find out they're less effective while overdosed, maybe.

Overdosing on, say, iloperidone would be a tad counter-productive. Especially the part where you throw up, stop breathing and pass out.

Can the character's dissociation suddenly increase dramatically? Like, doubled value under extreme stress.

Kinda. Killing people can massively increase it, as an example. Made worse by "visit location where you killed a human enemy" and "visit location where you commited murder" both being ghost triggers. (Soulless husk and vengeful spirit triggers, to be specific.) So visiting a place where you killed both human combatants and noncombatants (an act that'll cause massivr dissociation by itself) can end up with you seeing both of these varieties of ghosts and possibly more than one of each.

There (probably) is a life meter as well. Does dying have an impact, and how could surviving death be justified?

In singleplayer, you revert to a checkpoint. In multiplayer, your character is banned from the server snd reverted to the state you last saved them in. (You can pick one of your other characters, or else change servers, but that character is dead on that server forever..)

In the case you'd just die and get a permanent game over, I'd have to wonder how long players are expected to survive.

I don't know. In singleplayer, that depends on their actions. In multiplayer (if present) that depends on how the players interact. I suspect multiplayer lives will be short as I suspect that the players will only communicate through the movement of metal through each other's bodies, regardless of what other methods are present.

Would multiple hallucinations trigger all at once? Or were the cues you mentioned already covering that, like you'd only see one, with a % chance.

If you have more than one trigger in one place, sure.

Is the dissociation ignored at any point? Is there a cue when the character always acts sane? You mentioned there's no story, so maybe this was avoided.

Since when was there an off switch on crazy?