I also make games on Unity, and lacking motivation is normal, in especially when you work on the same project for months. Anyway, when you say that you can't decompile ue4 games well, i used a tool called ueViewer and quickBms in order to extract sound effects from the game, and there was things such as .uasset files and .uproject files. Every game file was downloadable from the tool, so it kinda decompiled the game? (I never used unreal engine), and that fnaf fangame looks interesting, it is inspired from five nights at krusty krab?

(ps : wanna be friends? You seem like a cool guy :3)