I reviewed the Task Sequence (for which thanks a million!) and I believe the reason for 'error 87:parameter is not correct' in two of the steps you disabled for the time being is the wrong dism parameter:
DISM.exe /image:%OSDisk%\ /Set-UILanguage:%OSDUILanguage% that should be-> DISM.exe /image:%OSDisk%\ /Set-UILang:%OSDUILanguage%
Similarly Set-UILanguageFallback should be changed to Set-UILangFallback.
I did not have enough time to test that one myself yet but according to DISM documentation Set-UILang is the parameter name that exists.