The dev fixed almost all the actual bugs I had been fixing via the mod for the last few updates, so those are done.
The biggest issue was the way the VN had been built for the original Ep4 which didn't use the original VN's core files resulting in save file point markers being reset (making old saves not load proper). This is resolved for the most part, although there's bound to be a few outliers.
Regarding Ep4's content only, the difference between this "Steam" version and the original non-Steam version is that the VN's core file for Ep4's content script is different... meaning those save point markers aren't the same. So, if one used my personal Ep4 mod update previously, made a save during the Ep4 content (content after Ep3), updates to the latest version of the VN, loads that save, then there's a good chance of rollback at a minimum. This is why I made the post
here.
So, is the VN 100% sorted? No, it now never can be at this point. We have to deal with what we have in front of us. The past is behind us.