Oops yeah, I had another look at your screenshot, you've already got his kernel installed, and the ram is right.
I just tested, you don't even have to unmount the swap partition, just delete it and the extended area (which doesn't look like it's even formatted, it's just a blank partition) with Disk Utility, it should leave you with 10.9gb free. You'll get the error if you delete them in the wrong order (i think), but it doesn't matter. Just create a 2gb partition with the free space and make it a swap area, easy to do. And make another partition with the free space. It won't be part of your main partition, merging it would probably be too irritating, but you'd have your space back.
STOP! Before you ask questions... READ the first post! RTFFP = Read The F*cking First Post
Yes, A 3.55 "jb" (cfw) is available, no >3.55 "jb" or cfw yet.
Yes, A 3.55 downgrade is available. But not to lower than stock firmware! (What it came with)
No >3.55 downgrade is out there yet.