There needs to be a setting to turn off the Demolisher from spawning like crazy in the early game when on Vulcanus. Also, even though underground attacks are turned off, they keep attacking underground and will ignore every defense I have. Turrets do not stop them or cause them to go above ground early.

"Also, even though underground attacks are turned off, they keep attacking underground and will ignore every defense I have":
I need your save where the underground attacks are disabled but still moving towards the base. Otherwise I can't fix the bug that it's not reproducible.

p.s. Rampant's underground attacks always leave a trail on the ground. If there is no trail and the biters just appear somewhere in the base, then it is not a "Rampant Fixed" attack.

Regarding demolishers: at the beginning of the game you can specify any time and evolution for their attacks to start. The default is 2 hours + 25% evolution. 25% evolution is a lot of time. But if you need more, then specify another value. You can call this menu from the player settings.