5.The drive led on the A500 keyboard is always on, even if there is no floppy inside and the led of the drive is always off even if there is a floppy inside. (I have my A500 in a tower)
Probably not too helpful but I'll just throw some ideas your way...
Since your A500 is in a tower, what are you using for a power supply?
What is your keyboard setup?
Have you checked and double-checked all of your power supply and ribbon cable connections?
I seem to remember seeing that "df0:

? df1:

? df2:

? df3:

?" once many years ago, but can't remember what the cause was. Maybe it thinks your trying to change all the disks at once, so to speak. Backwards cable maybe?
I'm assuming you have a hard drive and it's booting since you can see workbench, etc.... what happens if you leave the floppy drive cable off all together? Do the symptoms change?