2023-07-14T15:46:56 0.153 INF Command line arguments: C:\Program Files (x86)\Steam\steamapps\common\7 Days To Die\7DaysToDie.exe -force-d3d11 -UserDataFolder=C:\Users\Jack Stanley\AppData\Roaming\7DaysToDie\Mods -logfile C:\Users\Jack Stanley\AppData\Roaming\7DaysToDie\logs\output_log_client__2023-07-14__15-46-24.txt
UnauthorizedAccessException: Access to the path 'C:\Users\Jack\Saves' is denied.
It looks like an issue with your windows user name, because you have a space in your user name.
For a quick workaround you could create a folder with this name:
C:\Users\Jack\Saves
This may help you (not tested...)
Or just remove that (non-default) parameter from the command-line within Steam:
-UserDataFolder=C:\Users\Jack Stanley\AppData\Roaming\7DaysToDie\Mods