So going by the evidence - they didn't find any of Nevill's blood in the bedroom so you're assuming it was there. However, they did find some outside of Sheila's room so we KNOW he was there. I said I accept that he DID enter the bedroom but NOT all the way in.
They tested the blood in the hall they didn't test most of the blood in the bedroom. The bullets and casings prove the shots were fired in the bedroom while he was in the bedroom. His left profile was facing the killer during all 4 of these shots. The location of the casings suggests he was on the bed. The fact 2 of the shots had to have been delivered while he wasn't standing supports him being on the bed. The blood in the hall at most proves he walked into the hall after he was shot in the master bedroom but we already knew he walked into the hall because he had to in order to get to the kitchen.
Since Jeremy and the weapon were covered in Nevill's blood after the beating the blood could have dripped in the hall from such manner we don't know it came directly from Nevill. That could be why it was only a couple of drops. The drop near Sheila's room could have been dropped by Jeremy as he was going inside. Otherwise Nevill walked in that part of the hall at first but then turned around and ran down the stairs. It is crystal clear he wasn't injured in the bedroom Sheila was staying in and thus the notion he bled after leaving Sheila's bedroom doesn't work.
Either he bled there after leaving the master bedroom or the blood dripped off Jeremy after the beating.
Nevill was shot 4 times while in the master bedroom.
June was definitely shot 4 times in bed and then 2 more times either in bed or as she was getting out of bed/just got out of bed. This is 10 shots the notion Sheila was shot the same time as June and Nevill is fantasy. She was shot after Nevill was killed in the kitchen and the boys were as well.
June was shot between the eyes after walking around the bed to Nevill's side then going back to the door. It is unclear whether this shot came initially or after Nevill was killed in the kitchen. Most likely it was after because it is hard to imagine her walking around the bed through the killer 2 times at all let alone while the gun was still loaded. Most likely he shot her between the eyes after the kitchen episode.