hi guys I'm new! I was thinking that Midori could be the little daughter of the woman who got fired by the old man many years ago.
I also think that probably the old man's scream they heard was recorded from that TV show Goro was watching on the PC, that's why they were all together when they heard the scream. The victim was already dead
the light bulb in the childs room probably was broken with 3 bullets shot from the air gun, while the balloons popped because of some ice thrown at them
Midori may have used her nails or maybe some ice to cut the others. Then the ice melted and they found nothing