Sorry to hear about this! If you didn't have access to the healing skills I definitely wouldn't expect you to be able to get past Mitchell. Unfortunately, I wasn't able to replicate this issue after testing it on two different computers.
One potential issue I can think of is to make sure you've looked in the "Special" menu of the battle screen, that's where all of Caroline's actions are available. The "Items" menu as is intentionally left inaccessible.
As for the save file, it does look like an autosave from when I was testing was included in the download, thanks for bringing that to my attention (woops T_T). When you start a new game, the new autosaves will overwrite it, so that part is expected. It should be autosaving before the fight with Mitchell though, so there should always be a save to avoid talking to the npcs again if things are working as intended.
Thank you for the feedback though! It's always nice to have people try my games.