Interesting question because there could be so many answers.
Let's say that CF cards do not always "present" themselves as IDE drives and may say, "I'm used in a camera, or digital video recorder." This is why there is the TrueIDE device by icomp.de; it says they are all IDE hard drives. So try a few other CF cards or get one with WB 3.1 installed from Amigakit.
Now the hardware could be more up to date:
Your 6.6 ROM's are not the latest (Ver 7.0)
Your Western Digital controller is a Ver 4, not version 8, nor an AMD.
Finally, if you have version 3.1 Kickstart ROMs, you don't need a "driver" for the A2091. I'm not sure about why it hangs with Autoboot on, I'd have to ask a few more questions.
As for the AztecMonster, you will have to wait for someone with experience with that to chime in.