OK, so I've come up with a list for speedrunning the demo in an optimal route for 1) getting every item, 2) solving the Dirty Coin puzzle, and 3) getting the Good Ending. I don't know 100% if this works but I'm going to try it tonight when I get home from work. Let me know if I missed anything.
Edit: This route does not result in being able to trigger the Third Giggle; don't know why yet
> Pull chain in fireplace, then go into crawlspace and grab Fuse
> Exit crawlspace and put Fuse in fusebox, then leave room and go through infected door on the right
> Grab Blank Notebook from table drawer in hallway
> Turn around, exit infected door and grab Dummy Finger from table drawer near clock
> Go upstairs, press button, then go upstairs into attic
> Enter door on the right and grab Basement Key off table
> Grab Celluloid Object from behind TVs and combine Dummy Finger with Celluloid Object to create Dummy Hand, then read message on wall for
First Giggle
> Go downstairs to first floor and point Dummy Hand at fallen bookshelf for
First Murder Scene
> Go into cow slaughter room and grab Bolt Cutters, then cut chain from dresser and grab VHS Tape, then open pot in kitchen (just in case it has something to do with anything)
> Go upstairs into attic and down the dead-end hallway, looking at boarded-up lit-up door for
Second Giggle
> Go downstairs to first floor and enter infected door, then unlock basement gate and go downstairs
> Grab Lockpick from furnace, go through door, then point Dummy Hand at body on gurney for
Second Murder Scene
> Grab Valve, press X on door, back up and put hanging body between you and monster, kick body into monster, then kick the door twice to escape
> Grab Bullets on staircase, then go back down into room, grab Attic Key from shelves in the back, then run back out of room and upstairs
> Grab Bullets off shelf in hallway before going into bathroom, open drawer to grab Bullets, then grab Bullets from inside medicine cabinet
> Place Valve into pipe, then flush toilet and grab Handgun
> Exit through infected door and go into kitchen, then use Lockpick on drawer to get Axe
> Go to staircase and swing Axe at painting of woman with a bag over her head (or shoot it with Handgun) to get
Third Giggle
> Go into room under staircase with voodoo dolls hanging from its ceiling and use Dummy Hand to point at boarded-up door to get
Third Murder Scene
> Look at black mirror outside voodoo doll room, then press left control stick down and circle button to do a quick turnaround for
Fourth Giggle
> Go upstairs to attic, then use Dummy Hand to point at intersection of blue and white wires above bed for
Fourth Murder Scene
> Use Axe to destroy box with yellow tape next to bed and grab Bullets, then crouch next to bed to grab Bullets
> Go downstairs to first floor and enter TV room, then insert VHS Tape into VCR to enter
VHS World
> Walk onto porch and look left over railing for Ghost No. 1
> In hallway, when Pete says "What's that?" turn around to look back toward door for Ghost No. 2
> In kitchen, open pot, then look out window near microwave for Ghost No. 3, then crouch between fridge and microwave to grab Lockpick
> When Pete walks out of kitchen, look up above doorway for Ghost No. 4
> When Pete shines flashlight at staircase, look at staircase for Ghost No. 5
> When Pete shines flashlight in voodoo doll room, look inside voodoo doll room for Ghost No. 6
> Go into crawlspace when Pete pulls fireplace chain and go down ladder Ghost No. 7 may be visible just as you go down the ladder
> Back in the real world, go into crawlspace and look to the right to grab Front Door Key
> If you didn't see a ghost in VHS World, you probably should watch the VHS Tape again to try to see a ghost; otherwise, continue on with directions
> Go back through infested door and downstairs into the basement to where the Attic Key was, then crouch down and look at the doll on the ground for
Fifth Giggle
> If Fifth Giggle doesn't trigger, go back upstairs and watch VHS Tape again, hopefully seeing a ghost this time
> If Fifth Giggle did trigger, go upstairs and into kitchen, then point Dummy Hand at pot to trigger
Fifth Murder Scene
> Go upstairs to attic and open bloody door next to message on wall, then examine sign on rocking chair and grab Dirty Coin on it
> Exit the Dirty Coin room and go up ladder, then use Attic Key to escape the house
No, he couldn't get the third giggle, which prevented him from proceeding.
Oh, I get what you were saying now. He intended to get the Attic Key when he went downstairs for the Fifth Giggle, but never got that far because the Third Giggle wouldn't trigger for him, which probably was because you have to get the Attic Key to make the Third Giggle able to be triggered.