If the computere is not connected to the internet (which is a good choice), you can use some kind of media (e.g. CD, USB device, ...) to copy the log file (C:\Windows\wsusofflineupdate.log) or the cmd-window's content.
I understand, that you're frustrated, if it didn't work after 12hours of trying. But you have to remember, that all of us are doing the support in this forum in our free time and in that case 7h is a fast response.
It is correct, that wsusscn2.cab has some kind of bug, but it does not apply to all versions of Windows (AFAIK at the moment just Windows 10 1709 (16299) x64 is affected (
viewtopic.php?f=7&t=8044#p26011)).
wsusou does not include the option to download upgrades (maybe you misunderstood the "service pack"-option???).
viewtopic.php?f=7&t=7440Why I wanted to see the whole log?
Because often errors only make sense, when seen in context.
At the moment I wanted to see the OS build (e.g. 10.0.16299.15), the licensing channel (e.g. RETAIL), the edition (e.g. "Core", "Professional", "Enterprise", ...), the KB-numbers with their error messages and the updates wsusou attemped to install.
But all of this just makes sense in context.