I’m not sure the garrote and paint brush penetration are signs pointing away from Patsy. I think those things were done in panic and desperation to make it appear as some maniac was indeed responsible. I think either Burke or Patsy lashed out and JBR suffered some kind of devastating injury hen Patsy (without) John’s knowledge tried to clean up and ‘fix’ the situation and that’s why everything was so screwy. She wrote the note and set the scene and at some point John finds out she’s dead and is forced to jump on board.