These rules look great! Thinking of using them to play 1920s Lovecraftian horror. The character's occupation grants Advantage to one or two job-related skills. Seeing sanity-blasting sights requires an Int roll over 12, or the HD challenge rating of the Lovecraftian monster. If failed, the character takes 'mental damage' off their hit points. Not adding any rules, just interpreting Sanity loss as hit point damage as one's mind is shredded by alien visages, vistas, and concepts.
Sounds great, mate. I have been working on something similar although with more pulpy Robert E Howard/Brendan Fraser Mummy style fear rules. The other main rules additions are autofire weapons for things like Tommy Guns and a Hard to Kill rule for Eldritch Horrors. Basically roll damage as normal– if the result is 6+ you do 2 points of damage, otherwise you do 1. It works surprisingly well, particularly if you don’t tell the players about it.