Okay, finally able to get back at it after a three-day interruption.

Symptoms:
Near constant avast! Web Shield threat popups, even when running the anti-malware programs MBAM and OTL.

Clicking on link results in Google web searches often redirected to various antivirus/antimalware sites, but direct address entry in Internet Explorer 11 do not redirect.

avast! Web Shield popups most frequently contain:
under Object: various, often including text like “click.php?=click”, “redirect_js.psp”, “credit cards”, “debt management”, “cleveland consumer co” etc.
under URS: Mal
under Process: Users/John/AppData…WINFB36.exe

Ran MBAB as instructed, log attached. No threats found.
Ran OTL as instructed, program generated OTL.txt (attached) but not Extras.txt.

Posting this now, will proceed with aswMBR.exe

Behavior continues