I don't have as many options now for the appearance so everything is so small. The folder icons are ugly. I could just cry. These size of the tabs on Firefox are so small I have to use Control+Scroll to make everything large enough to see.
I believe if you do an internet recovery (hold down Command+Option+R), that should install the OS that came with the Mac - at least that's what happened to my MBP when I did that.
Even though I have yet to experience El Capitan I can understand your dismay. I accepted the free upgrade on my Gateway pc from windows 7 to windows 10 and I totally hate it so that is why I decided to give Apple a try. I'd love to see my new iMac but UPS rerouted it from here to Denver and now it's on it's way back here. Maybe I'll yet see it this week sometime. I hope maflynn's suggestion works for you.
Internet Recovery may be a problem since your 2008 iMac originally shipped with OS 10.5.
Here is a quote from the link above in the Internet Recovery section:
"Some Macs that came with OS X Snow Leopard can use Internet Recovery after installing OS X Lion or later and a software update.'
Hopefully you have a complete backup of your OS 10.6 system.
I don't have as many options now for the appearance so everything is so small. The folder icons are ugly. I could just cry. These size of the tabs on Firefox are so small I have to use Control+Scroll to make everything large enough to see.
I assume you're talking about the slightly thinner font. If getting used to it is not an option, there is a solution which doesn't require you to downgrade your OS. Reverting the folder icons is also possible, but requires a backup of the older icons and temporarily disabling System Integrity Protection.
Why would the OP need to downgrade to 10.5 and then upgrade to 10.6? A retail copy of Snow Leopard is all they need to downgrade to 10.6, but either way it won't install on top of El Capitan and will require a clean install.