Unless you have an accelerator in the A2000, you can't expect to get it working on it. IIRC the graphics software needs a 020 as a minimum.
Forget CGX v3, it doesn't work very well. There is a reason it has been updated. Get Picasso96 from
http://www.aminet.net instead, you will find version 2.0 which works just fine. Get SnoopDos as well, as it might tell you what goes wrong when booting.
Install Workbench again. Make sure you have a 68040.library in libs:. Install the Picasso96 software (don't unarc it on a PC). After installation, check that you have a Picasso96Settings in devs: and a CV643D monitor driver in devs:Monitors. Start P96Mode in the Prefs drawer, and use the menu to add the screenmodes to the CV64. Select a screenmode and test, and the monitor connected to the CV643D should display a test screen. Save the settings, reboot when it asks for it, and reboot. If all goes well you can select a CV643D screenmode in the screenmode prefs afterwards.
-EDIT-
I just saw that you had a 030 in your A2000. Maybe the card is dead afterall; bummer :-(