I noticed that you are running fcp 4.5. Upgrading to qt7, while possible, is not advised unless you upgrade to fcp5 & Tiger. I’d stick with another codec until you are ready to take the plunge with Tiger & FCP5.
No, you don’t need QT Pro if you are on Tiger & FCP5. QT7 will upgrade to pro automatically upon installing fcp5. You can then use compressor to compress to h264.