Thanks for finishing the game Garry!
The scoring is a mix of points for finishing parts of the game, points for doing various things to prepare for the guising sequence in the care home, different points for different ways of getting past puzzles, different points for different paths in the manor and different ways of getting through those, secrets that can be found in the Reids' house... there are a lot of permutations. I don't want to post spoilers on the public comments, but I could PM you a detailed breakdown if you have Twitter or something similar (annoyingly Itch doesn't seem to have a private message function).