Your original configuration looked okay so you were close and we could have got to the bottom of it. I may wrong but I am sure import is only for Server_cfg.ini files not manuals!
You need to get back to the point where acserver.exe runs (even if you cant connet) and we can go from there. The values you entered in the video looked right. Just for clarity acservermanager is not acserver. All acservermanager does is make editing Server_cfg.ini easy.when you click export you have to browse to the location the new configuration will be saved to. This location is where acserver will look for it (server_cfg.ini). On my 64 bit machine it's C:\Program Files(64)\Steam\steamapps\common\assettocorsa\server\cfg.
On a 32 machine it will be C:\Program Files\Steam\steamapps\common\assettocorsa\server\cfg.
The save button simply saves(but does not export) the config you are currently editing.
When you click run in acservermanager, acservermanager runs acserver and acserver looks for Server_cfg.ini.