First thought - get a new scanner. The PRO-92 is notorious for being essentially deaf at 800MHz, and not much better on the other bands.
Pick up a PRO-97. I was on sale through today for $150. It has all the same features of the PRO-92, a more sensitive receiver, more characters on the text tags, 100 channels per bank, Signal Stalker, and other improvements. And it works essentially the same way.
Another idea is to get an antenna that's designed for the frequency bands you're most interested in. If you're most interested in VHF/UHF, consider the Diamond RH77CA. If you're more interested in 800MHz, the RS 800MHz duck antenna is a popular choice (and it does okay at VHF, in my opinion better than the Diamond at 800).
I'm not aware that Kershaw County FD/EMS/SD/PDs are on an 800MHz system, correct me if I'm wrong. You seem to indicate that you've programmed a trunked system in your post (primary and alternate freqs). If you're programming Palmetto 800, pick the site closest to you, and program all that site's frequencies. The PRO-92 requires all frequencies from a site be programmed. You're hearing the same conversation on multiple frequencies probably because they are frequencies from different sites carrying the same conversation.
So, if you're most interested in Kershaw Co services (as opposed to state or adjacent county services on Palmetto 800), consider the Diamond antenna. But a new radio will do wonders for you.
Brian