Hi back ;-)
Don't know about the keyboard, but on the external FD, yes, any external Amiga drive is plug-n-yes-it'll-work-just-fine. I've got three externals on mine, I think that's about the limit.
On the video, how about using the composite output from the MB or getting an A520 adaptor? I used and still use the composite output from mine (now a 1200, but the 500 what's place it took isn't too far away), running into the back of my big Sony receiver, and from there running into the composite inputs of a 1084, a 1080, and a 1702 (all old Commodore monitors, but anything with composite input would work - like your VCR). Back in the days before adding the deinterlacer I would keep one at the foot of the bed, and the other two on the desk. People would say "Why do you have two monitors?" and I'd reply, "Well, I have two eyes, don't I?" :-P
Best of luck in your project,
Mike
