|Your #4 probably came overlapped with my #3 which I was editing. I would be interested to know, in a nutshell, what you did to fix it.|
For the future I would recommend you keep onboard either MSE AV (as mentioned) or Avast - both are free and good. Opinions abound and there are pros and cons for both. Neither are heavy on resources.
Glad to hear problem resolved.
Always pop back and let us know the outcome - thanks