what the heck is up with my soundsystem?

There is a seaperate cable that goes between the cassette and CD players. Might check ebay as it appears yours is not present...

I'd take a trip to the junk yard. Ford might be able to order one, but they will want your first- born for it... This auction has the cable you need in the harness http://cgi.ebay.com/ebaymotors/Mach...32764QQitemZ260386432764QQptZCarQ5fAmplifiers

The deck you have is not the factory unit, which is why the cable is not present. Also, the jumper plug is still in the back of the deck where the CD player harness would plug in indicating that there was never a CD player ever hooked to that deck. The large plug is the power plug, and the smaller plug is the speaker plug that goes to the factory amplifiers. If you have no sound from the rear there could be several reasons. If the tweeters don't work, it could be that the rear outputs on the tweeter amp are bad or the speakers are blown or missing. If the woofers don't work it could be the same reasons as the tweeters, bad amp or missing speakers. If all the factory gear is there but there is no sound at all from the rear it could be a bad deck, hacked wiring as it appears that someone had different gear in the car at some point, or the fader is set to the front. It sounds stupid but over the years I've "fixed" the fader for customers MANY times who thought something was broken and didn't realize the fader was set all the way to the front.