Hi Ben,
Photo Mechanic's Export option from the preferences will save all of the IPTC Metadata Template's popup lists, field contents and Snapshots. Once you have confirmed that the new preferences have fixed the problems you were having with the Slide show, you could Import these settings back into the new preferences.
You can go back to the original preference folder and then use the Export option from the Preferences to create the PM_Export.PMX file. Then switch back to the new preference folder and then Import the preference export .PMX file.
With Photo Mechanic quit, go to the ~/Library/Preferences folder. Rename the com.camerabits.PhotoMechanic folder by appending -new to the name. Now remove the date that was appended to the end of the original com.camerabits.PhotoMechanic folder.
Start Photo Mechanic and it should look like it did before the preference reset. Go to the Preferences and click the Export button. Save the PM_Export.PMX file to the Desktop. Quit Photo Mechanic. Rename Photo Mechanic's preference folders back by removing the -new from the fresh one and appending the date to the older one.
Start Photo Mechanic using the new preferences. Go to the Preferences and click the Import button. Locate the PM_Export.PMX file on the Desktop and Open it. Click the Import button to continue. A Warning message will open next. Click the Yes button to complete the preference settings update. Photo Mechanic should be restarted. Now you should be all set with the IPTC Metadata Template configuration as well as other settings. The Favorites panel entries are not saved in the Preference Export file.
Best regards,
--Bob