Glad you remember at least.
Gee doesn´t have to type anything, you know!
Your scenarios have loads of holes and errors as well, Adam, none of us know what happened that night.
A shortened version
Jeremy cycled/walked to WHF at 2am.
Got in through a loosened window. Picked up a fully loaded rifle.
Crept upstairs. Shot June and Neville 11 times in/by their bed.
Neville gets downstairs. Is followed and brutally beaten and shot again. Dying.
Sheila is lead or carried to the main bedroom. Or had already woken and retreats to the far corner. She is shot and killed.
The asleep twins are killed.
The staging of the scene to make it look like murder/suicide takes place.
Jeremy exits out of a window. Banging it locked from outside. Then walks/cycles home.
Simple.