I have a std (hp) c compiler and you are correct that the tape drive is connected to this (HPUX 7) system. I don't have anything else with an HP-IB interface, although it appears that you can connect it to other devices (there are PCI cards for this connection type, but I don't have them).
1) I used to write, maintain and port c pgms on HP_UX (ANSI, std (hp) c and ProC) so I hope that won't be an issue.
2) I don't know the details yet, but I have found some interesting reading that seems to indicate that they are fixed sized records ->
http://www.access-one.com/rjn/computer/hcdvsqic.txt
"16- and 32-track tapes are preformatted by 3M or a 3M
licensee. A full-track factory write head lays down fixed
physical records on the tape. No 16- or 32-track end-user
drive ever writes on these record headers (called "keys");
only in between them. HP "format" and/or "mediainit" user
processes merely "certify", performing read/write tests,
sparing bad blocks and updating logs."
...which would mean that a dd would be able to capture the tape information correctly?
I checked the tape drive today and found that the pinch roller appears to be ok - it felt a little tacky, but not gooey, I will try it with some backup and other tapes that I have, before I attempt anything with the HPUX install tapes.