Boots from open firmware, can't repair drive otherwise

I have a Mac OS X 10.4.11 iMac G5 1.8 Ghz (original). If I go to open firmware and type mac-boot, it boots fine.

I'm using one of those flat key Apple USB keyboards with numeric keypad, and a Microsoft Mouse.

Occasionally the keyboard becomes non-responsive, unless I force quit the Finder.

If I attempt to boot on its own, it stalls at the Apple logo and won't go further. If I boot into single user mode it can't repair the file system.

So the question is, would replacing the PRAM battery make it able to boot without going into open firmware?

Or do I need to repair the directory with a good version of Alsoft Disk Warrior which I have to dig up from my old cabinet?

Do I need to get an older keyboard?