Regarding the inquisitor, I only urge caution.
No worries and I appreciate the words of warning. Actually, sort of going through it, writing it out, and explaining it helps me to make sense of it everything. Constructive criticism is always welcome; after all, I am new at this

A thought I had at lunch was that perhaps the inquisitor could arrive, investigate the party, and then enlist their aid in rooting out the corruption within the church (after all, they are more capable than the average individual). So the PCs find and expose the more obvious parts of a cult within the monastery, but remain ignorant of the demonic master that has been resurrected. The inquisitor will burn the "leader" and tell the PCs he has urgent business elsewhere. Shortly after he leaves, the PCs stumble upon a new clue or fact that reveals that the true horror is only just beginning. Just when they get to the bottom of it, all hell breaks loose.