Ther's an an old tutorial for E-UAE that might help here -> http://www.rhythmiccanvas.com/person...UAE/index.html
For the uaegfx problem this is the advice given.
10. Wait while the installation continues. When the Display Mode Preferences window appears, select your desired screen resolution and bit depth (eg. uaegfx: 800x600 15bit). Then click Save (do NOT click Use).
I'm assuming you are using the MacAIAB-r10c.sit archive. If not let me know and I'll drop it here.
Try the above first.
Also the old AIAB MacUAE tutorial here
advises that the copy-files.script should be replace as well as three others.
Hope one of these tutorials has the answer as I don't have a Powerbook to test this on.
Sooooo.. will there be a christmas gift for us?!
This is looking unlikely, but I may yet be able to pull it out the bag, all I need is a few miracles.