Can you permanently change anchors for a set brush?

Yes, you can. If you click on the center of the transition widget (the white sphere) with the middle mouse button, you can move the pivot If you hold V while doing it it will snap to vertices. You can then make the change permanent by right clicking the actor, going into Pivot and selecting “set pivot offset” (or something like that), so it will remain even if you deselect the actor.