Played up to the end point of the demo of all of my favorite characters and now none of those saves work so i have to replay all of them :(

Do you mean the current demo which contains Episode 1 only? Or the previous version of the game which was Episodes 1-8?

We have had some coding changes which means old save files are not compatible with the new 9.1 update, so yes, you will have to replay, however you can use the skip function to play through to the new update a bit easier.