itch.io

Then it would be best to download it directly via browser, unzip it and start it with the .exe.

Since TM uses the renpy engine, savegames are duplicated in a central system folder, so playing from a different folder should still show all savegames.

You could also try to locate the app folder in which itch installed TM and replace the files with the ones from the direct TM 1.0 download, but I can't guarantee that this would work flawlessly, so solution 1 is still the safer approach.