>(1) Is it possible to have 6 databases, each with many tables, open and running as part of one project? As I understand, only one db can be open at one time.

Yes, you can work with several databases. You can have more than one database open, but only one will be "active", or selected, at a time. See SET DATABASE.

>(2) Is it possible to have running, more than one executable and each executable exchanging information with the other?

Yes. One way would be for the executables regularly (with a Timer) checking for information on tables, or in other files. For a more immediate communication, perhaps something can be done with the Windows API - but I don't know the details. I hope someone else can give you better information about this topic.
When a thought of war comes, oppose it by a stronger thought of peace. A thought of hatred must be destroyed by a more powerful thought of love. (From the Writings of the Bahá'í Faith)

Thanks for the reply. I don't mind exploring, so I shall proceed with vigor.