Hi Ellen, I'm afraid this
http://www.jointech.com.hk/upgrade.html is the only firmware that is available for the JE 100. They do not have previous versions so that you can rollback your device.
Were the kbd and orientation issues apparent on the original JE 100 firmware and version 3.0 of eReader, or had you not tried that combination?
Why can you not use eReader 2.6, do you get errors when installing? There may be some support files missing from the JE 100 after upgrade that we can replace.