The missing battery will cause the Plus to loose it's date/time, startup disk and various other settings when you unplug it. It can cause weird behaviour, plus it's a bit of a PITA, so I'd replace the battery. Other than that, I'd try a fresh format of the drive and a fresh System disk and see if that helps. You can get a clean copy of 6.0.8 here:
Disk 1
Disk 2
Download those, install them on the hard drive and try booting with just that connected (no floppy in the drive)... hopefully it should boot [
] ]'>
Disk 1
Disk 2
Download those, install them on the hard drive and try booting with just that connected (no floppy in the drive)... hopefully it should boot [
] ]'>