what do you think....?

i assume burke heard noises in the bedroom and investigated. i never thought of sexual abuse by burke.

That theory is way more than a stretch considering there is not one shot in the movie that implies he is a pedo or even knows about Reagan. He's a drunkard and perverse but that does not mean he'd be attracted to kids.
It states Burke would not have a reason to go into the room. Well the obvious scenario is he heard Reagan crying for help. She was sedated but she can also turn her head completely around without dying, so clearly the demon would be able to handle drugs.
The symbolism of the head being turned around and the desecration of the church are all parts of black mass. The film stresses Reagan's father being absent hard, as an excuse for her being isolated and playing with the Quiji board. The little red riding hood art is much much more easily connected to the demon than to Burke.
In the novel Kinderman is suspicious of Karl and there is something going on with Karl's daughter being on drugs, can't remember clearly enough.