Stuck: Need Disk repair but DVD drive dead and only have USB 1

Question

[1 Ghz flat-panel iMac with USB 1 ports (no USB 2) and also Firewire 400]
I noticed a strange discrepancy (small but concerning) between the size of a folder on hard drive (folder of all mp3's with no subfolders) and the backup of the same folder on a mounted thumb drive.
(The size difference was not due to any invisible .DS_Store files and both folders are displayed in List view format.)
Disk Utility reports three things:
1. Incorrect number of thread records
2. Volume Bit Map needs minor repair
3. Checking volume information.
          Volume free block count",0)   [I might have mangled this line]
(It should be 13438611 instead of 13437937)
Here is the GOOD (but these are useless as explained under the "Bad"):
- I have a Tiger 10.4 boot DVD for a repair ==>but see below
- I also have a Disk Warrior disk (never used)
Here is the BAD:
- My built-in optical drive [Pioneer DVD-RW DVR-105] is -- I now discover - defunct and DEAD - it does not run the Tiger Boot DVD (in pristine shape).
- I bought an external SuperDrive (unopened) but I believe no boot from USB 1 is possible in PowerPC so a SuperDrive with USB 1 is useless.
Questions:
1.) Is there any way to boot from some external source (optical drive is DEAD) to run Disk Utility and/or Disk Warrior? -- I see none in this case! (gulp).
2.) More importantly (and this is my fundamental concern): Do the three Disk Utility hard drive issues constitute any direct threat to the integrity of my files?
I have almost everything backed up to duplicate thumb drives over these many months as standard practice.
Are these Disk Utility errors fully isolated to hard drive directory-keeping...or do these directory damage errors pose the possibility of mangling or harming my files or their metadata (filesize, etc.).
Put another way, when files are backed-up from a hard drive under the Disk Utility reports above, do they remain unharmed and undamaged by the situations reported by Disk Utility?
Thanks,
Bill

Answer 1

Jeff and Michael,
Thank you both for your generous and thoughtful input.
Michael: As I slept on it overnight, the exact same idea occurred to me of trying a Target Mode to the iMac from my Lion MacbookPro (I have it but stupidly have yet to use it much!).
I did buy a Firewire 800 (MBP) to Firewire 400 (iMac) adapter cable a few months ago!
CONCERN: Would there be potential compatibility issues or risks in running Lion 10.7's Disk Utility against the hard drive of the old OSX 10.4 iMac in Target Disk Mode?
==> Assuming an "it's ok" answer to the Target Disk question, would the majority of users agree that the Target Disk Mode would be more prudent than running:
fsck -fy   in Single User Mode
I have never done fsck -fy before especially because I was under the impression there were issues with Journaled drived but from what I have read today...it looks ok to do)
Jeff: Can't thank you enough for the reference to the OTW DVD drive. I might first invest $10 in one of those DVD lens cleaner disks that I've read about. It's probably not the issue or else why would the drive read commercial Music cds perfectly well!
Thanks,
Bilil