The Reverse Scroll Direction option does nothing, even if I restart the game.

This was actually fixed 1.5 years ago here: fa9b878, but I never released a new version with the fix included...

I've also abandoned that older Forge version, the current master branch is based on top of the newer LiteLoader port/code base. There are no builds of that version on CurseForge yet, I still want to rewrite and improve some things, plus I'm waiting to do some refactoring in malilib to get the final 0.10.0 version of that done first. But there are builds of that version here: https://masa.dy.fi/mcmods/client_mods/?mcver=1.12.2 with some new features that did not yet exist in the old Forge version. And note that you do need malilib as well for that new version (from that page).