There are no errors at all in the latest log. You mentioned that you are having the same problem trying to play on a different computer on the same network. So with no errors in the game log and two different computers having the same problem, that points to your network as being the source of your problem. Since your internet provider says that your connection is fine, that leaves your router as the most likely source. It still could be your antivirus even though it is disabled. Some antivirus software still have some functionality even disabled. So, first I would create an exclusion in the antivirus for both the the 7Days folder and also your save game folder in app data/roaming/7daystodie. If you don’t know how to exclude folders, instructions are in this pinned topic for the most popular antivirus software: https://community.7daystodie.com/topic/3998-support-faq-information-and-common-solutions/
Second, I would access your router and be sure to forward all the ports listed in that same thread. Once you are done, use an online port scanner to check that those ports are indeed open. Some routers are notorious for being difficult to forward ports. Also, some internet providers will not allow users to forward ports. You must contact them by telephone and have them forward the ports for you.
If all of that fails, I have a final suggestion to uninstall the game, clean the files and edit the registry. Let me know if the above suggestions do not work then I’ll walk you through the extreme uninstall process.
He doesn't need to forward any ports on the router if he isn't hosting a MP game himself.