It seems like you're facing an issue with the speed limiter not being disabled. Although you've tried several solutions, the problem persists. Here are some steps you can take to troubleshoot and resolve the issue:
1-Check In-Game Settings: Make sure to check the in-game settings to ensure that the speed limiter is disabled. Sometimes, finding the option to disable the speed limiter may require some research.
2-Inspect the Config File: Check the configuration file (config.cfg) of Euro Truck Simulator 2 for speed limiter settings. Open the config.cfg file with a text editor and verify the setting for "uset g_use_speed_limiter". If this setting is missing, as you 3-mentioned, you can manually add it.
4-Verify TruckersMP Settings: If you're using TruckersMP, also check the settings there to ensure that the speed limiter is disabled.
5-Reinstallation: If the above steps don't resolve the issue, consider reinstalling both the game and TruckersMP. Sometimes, this can fix file corruptions.
If none of the above steps resolve the issue, consider reaching out to the official support channels of Euro Truck Simulator 2 and TruckersMP for further assistance. Hopefully, your issue will be resolved soon!