I believe it is only fair to pose the position that, "If it benefits the progress of the character without detriment to the party, there is no reason one should not consider it."
The character, from my understanding might only be free in the sense that he is no longer actually "cursed", but the effects of the curse are not cured. There will always be some part of Xaron that exists, even if only memories and thoughts but not an "entity". It is one of those scenarios where the demon might be banished but is far from dead. Torus might both remember and know Xaron still, despite there being no actual control and domination. He could even believe the presence to still be with him from time to time or fall back into habits or routines of that other personality, even with it "gone".
Knowing these options and more, I see no particular reason the character should not make that decision provided they would make it. If Torus really does wish to be free, this would be that first step. The largest step, but that shadow of evils past will never quite disappear. Conditions that arise for the influence should be based on that; just how much remains.
Again, my only concern is that it is best for the character without costing the party. To give a simple but direct example, Torus does not suddenly forget how to cast his spells. Given this is a module and we are still quite low level by virtue of that, we haven't the luxury to piece together Torus' person as a side quest. A worthy one I think that would be and something I would be willing to do, but I cannot speak for anyone else. This story to my knowledge centers on what we can make do within it by the rules and what our Dungeon Master is willing to contend with in their game.