I've played your Backroom, and I definitely love it. That's why I said you're definitely know what you're doing. It's just the idea that is lacking.
I think FNAF style like this could also work without jumpscare by utilizing tension alone. You're actually on the right track with what you're doing with the Gabriel in the attic, I don't really consider that as a jumpscare, haha. It's a shame that I can't say the same with the rest of the encounters.
I'm really positive you can make something great. Really looking forward to your next stuff :)
You know, Mandela Invasion is my first point & click game and my first game in FNAF style. It was actually an experiment to see what I could accomplish and how the players would react. I wasn't very happy with the fact that my previous games had a lot of jumpscares. I wanted to scare players with atmosphere in those games, but unfortunately it wasn't up to me to add a lot of jumpscare. I try to learn something new with each new game and thanks to that my games evolve - they keep getting better. At least I think so, judging by the amount of positive reviews and YouTube videos.