To explain better than Late did, the problem isn't the mod it's that Week 1 was made with an oversight, which is using any custom font or textbox then deleting them will cause the game to crash without them. I helped them fix it in Day 8, so any version of the game after Week 1 won't crash if you delete custom fonts/textboxes.
So the problem is only with Week 1, so if you used the mod or added your own font/textbox in Week 1 then decide you want to stop using it your options are:
1. Reinstall the mod or custom files
2. Delete your persistent data from both of your save locations
3. Copy the fixed code file from the Day 8+ versions that fixes the crash to your Week 1 game, which I believe is the "game/gui/design/design.rpy" file