My A3000 is basically the same setup.
I've found that setting the boot device (your hard drive) to unit number=0 can help.
This is the first ID to be polled. Sometimes the SCSI controller gets unhappy and won't boot if it detects something like a CDrom first.
Even though you have your drive set to supply termination power, I'd check diode D800 on the motherboard is not open circuit and can supply 5V to the bus.
Play round with the termination a bit. I've seen really weird instances where termination is definately set correctly, but it doesn't work.
Try things like disabling MB termination and enable drive termination.
Download one of the many utilities from Aminet such as SetBatt and check all the SCSI contoller settings.
If in doubt, reset them to default.
Also make sure you don't have a faulty 50 way ribbon cable, try another one.
Enter the early startup screen and see if the new partitions are listed there (you should see DH0 or whatever you made them in the list).
If not, then they are not being auto mounted on startup, so go back and check your HDtoolbox settings.
Note that if HDtoolbox can actually see the drive, it's a good sign that the hardware is probably OK.
Failing all that, perhaps try a different drive. Some just appear to be not compatible with the A3000's SCSI instruction set.
