Solution to Avast question was supplied by Pondus.
Solution to Update problem found below.
Was in contact with Microsoft.
The solution was to create a batch-file out of the following code (I simply named it fix.bat):
SET ARG=%1
FOR /F "usebackq delims=" %%A IN (`dir /B C:\Windows\servicing\packages\Package_for_%ARG%~*.cat`) do SET FOUNDPKG=%%A
SET PKGNAME=%FOUNDPKG:~0,-4%
DISM /online /NoRestart /remove-package /packagename:%PKGNAME%
Then open CMD and do
cd %userprofile%
cd desktop%
fix KB1234567
When that's done, download the update and install it