Can I safely downgrade my Sony Xperia SP?

I just upgraded my Sony Xperia SP (C5306) with Sony's horrible tool from 4.1.2 to 4.3 (build 12.1.A.0.XXX to build 12.1.A.1.207), but my phone now runs worse, and I don't like the changes at all! Unfortunately, it seems there is no legal/official way to revert. I am not computer illiterate, but have no experience with rooting and such, and everything I read warns about possible bricking and whatnot, so I am a bit weary of jumping into something and breaking my phone. Is there something I can do that is safe to return to the old OS? I'm so bummed as I seem stuck with this OS and I've deleted all my stuff when I tried doing a factory reset. :( Thanks for any help!!!