Dear OP
I owned at least five of these machines.
The bent door/movable fan issue needs to be addressed. The casing on G5's is not incidental to their workability.
I always bought brand new hard drives for all models of the G5s. For some reason, HD's (and as you saw even the IDE superdrives) cause weird problems on the G5PMs if they are failing.
Also did you update to 10.5.8? I read you did 10 5 6 but not the full update.
I'd get a new ide Panasonic superdrive, heck you might as well get a blueray IDE if you can find it (there was some PPC Blu Ray workaround back in the day) and new hard drives.