I'm sorry to say that the OS you are running on doesn't support FCP 7. The last OS that fully supported it (officially) was 10.6.8...but it is known to work well up to OS 10.8.5. OS 10.9 is where things started breaking...Compressor and Motion stopped working. And so every OS version you go past the officially supported one, the less likely the app is to function fully. It was, after all, discontinued 6 years ago.
Advice? Find an older machine with older OS to run it on (you can't install older OS versions on new machines)... or find someone with an older OS and FCP 7 to create the credit roll for you, and export as a ProRes file.