Ok, I copied your contents into a new config.txt on my system and was able to open it in MyOSMC.
So suggest you copy and paste the contents of mine into a clean one on your system and try.
If you still have an issue I suggest to enable debug logging and upload logs after you try to edit it vua MyOSMC.
Here is mine working with your content. You can directly copy it on your system.
sudo wget -O /boot/config.txt https://paste.osmc.tv/ukawenecob
Check the contents afterwards with