I also use a product called PB Blaster from Auto parts store & have had good success. Spray it on let it sit for awhile & tap on the bolt to help it penetrate.
Once apart, you should just replace the fasteners with stainless (check strength markings) and clamps, after all they have been together for over 12 years...and use lock washers and anti-seize on the threads, you will be good to go...!
Spray it up as indicated above, and then you just have to get pretty rough with the stuff. Twist and turn it both ways and yank! Sometimes a rubber mallet can help if you can get a swing at things.