Thank you Steve and Helen.

I am finally able to backup and restore the database.

I am curious about the cause since it did use the secondary file before.

I am now using a page limit of 131072 at 8192 bytes for a 1GB file size.
This should give me some "buffer" space should the engine need to use it.

Copying all 3 files from the linux server to my backup server (running
windows), using the GLINK program, then running gfix seems to have
worked. Of course, gfix reported a few errors (where IBSurgeon did
not report any).