3: As I mentioned Weak Password could be more than the one you set, routers come with a default admin password, you can search the internet to actually find these admin passwords for the various router models. So if the default admin password is still present, it is a weakness.
4: If you found the Windows Defender Security Centre > Virus & Threat Protection Antivirus, your pretty much there. It should show the antivirus that is installed, Avast Should be listed and No Action needed (in my case as it is running). Does your show avast is installed and no action required ?
You could well have some other information if Avast isn't running (and Defender Antivirus is) or is out of date ?
As in my attached image there is a Windows Defender Antivirus Options and a down arrow to expand, that is where I found it. However if Windows Defender Antivirus is actually running, active not passive, I don't know if there would be any option to stop periodic options.
On BTW: occasionally I have an issue with the mouse (it just stops moving) on my XP system, sometimes that is down to low resources, but that does recover. I haven't experienced this on my win10 laptop.
Does your keyboard still work when experiencing this ?
If so try the three finger salute Ctrl+Alt+Del keys at the same time this brings up your Task Manager. This could give indicate if you have a resource issue, etc. and it should allow you to restart or shutdown. Doing a hard shutdown, electrical power off could well crash some programs (and possibly corrupt some running files), possibly why the avast tray icon wasn't there.
Note, I just wonder if you haven't got anything else going on with all these different issues (what that might be is the question).