You're welcome 
The AvastClear uninstall worked well. The 'Run' button was barely visible in the 640x480 Safe mode display, but I could click it.
The reboot after uninstall took a few minutes, hanging on a black screen until the login screen loaded.
After login Windows displayed the expected " The system has recoverd from a seriuos error .." popup, prompting to Send the Error report.
So far, I have a stable system again

, but no Avast protection

. Again, my sincere thanks.