Disclaimer. I haven't read all 5 pages, so this suggestion may have already been offered.
On any installation, the first security I install is Avast. The second, which I believe is most important is SpywareBlaster:
https://www.brightfort.com/spywareblaster.html. Update about once a week and Enable All Protection. Doesn't need to run in background. If this is kept up to date the odds are that the others will have less to find when scanning.
Then another anti-malware. I have been using Emsisoft, but my subscription is about to run out, so I will be switching to paid Malwarebytes, which is a one-off lifetime payment, and in my opinion a good investment, with one caveat. Malwarebytes is very (overly?) aggressive re PUPs. You do need to consider whether all the PUPs it offers to remove are actually unwanted.
I also have SAS Pro, but don't run it in background. But it's still useful as a manual scanner
Thanks to this thread, I shall also be installing CryptoPrevent