If activity seems to stop after 5PM like you stated in
post #4 that would likely rule out:
Oconee Hotel Company (WPPN903)
Northside Hospital Cherokee (WQZB642)
Sunbelt Forest Products (WRVY362): Per Google, company closes at 5PM Monday thru Thursday and 2PM Friday. Closed Saturday & Sunday
Bridgestone Americas per Google is open Monday thru Friday 8 to 5 & closed Saturday & Sunday
The rest don't disclose business hours. Hope this helps you narrow down possibilities. I've sat on certain stations I came across for months, sometimes years before I was finally able to pinpoint a license. Subscribers who rent from radio shops are often the most difficult to nail down. Keep listening to see if you can determine any identifiable info