The settings can't be changed once you save the game using this mod.

I can't reproduce this personally.

Same issue happens for me. Changed default settings, saved the game, removed and mod-zoom levels persisted after removal. Now I am having strange keyboard issues as well but cannot directly evidence it was this mod.

Changes persisting after mod removal is due to limitations in the Factorio API. Due to how the API works you'll need to use another mod to restore the settings, for example https://mods.factorio.com/mod/Zoom-reset