Alright, I did some messing around and I have been able to have small octopus spawn. The cultist content is reachable, but with some caveats.
1. if you cheat the "pollution" save file, you need to change the value to about 190ish, for it to reach 75-80 infection.
2. if you cheat the file early on, and then get corrupted by a small octopus, you dont seem to be able to pick up already downed survivors (like the ones already caught and downed by crabs and such.) You have to be able to talk to them. And you cant seem to revive them, if you are corrupted, atleast, not that I can see. So, if you dont have a safe house area, already filled with a few survivors, you wont be able to gain xp, to get all the perks. Of course, already banked AP roll over, but whats the fun of having all these abilities, when you cant use them?