1. Tristen said "Wittershins" (or whatever that word is) which Erica had told her meant "to reverse the evil" .. and so they reversed their video footage on the monitor to see hidden images of the night before.
2. Later Tristen actually spoke in reverse, saying "The children will again walk free" ..
3. A soaking wet Eileen Treacle (from the drowning in Tappy East Creek in August 1825) is seen by Tristen while she's in the hospital bed, walking in reverse.
4. The meaning of ESREVER (reverse) is to "go back" into the film to unlock hidden images, messages, AND a hidden meaning.
5. I haven't read the book of Rustin Parr's secret confession or watched the featurette "The Burkittsville 7", but from what I've gathered, he did not kill the children, but instead the lone surviving child, Kyle Brody, did .. and then left his bloody handprints on the wall.
6. The life of Elly Kedward is a sad tale of mistreatment and misunderstanding. Her new "biography" makes that very clear.
7. After reading the above posts -- and remembering what the "possessed" Tristen said about the children of Blair pressing their hands into her bloody wounds-- I do in fact believe these children were evil and their line may have passed down to Kyle Brody and maybe Jeff. But as far as Jeff being the one who hunted Heather, Josh, and Mike ..... I'm not too quick to jump on that idea just yet.