1 - if the db commands don't work, try learning them from the original remote. If that doesn't work try learning in RAW mode. If that doesn't work, call support. Sometimes they can change how the signals are sent to handle those types of cases.

2 - Device mode is meant to mimic the OEM remotes for each device. So device mode for the DVD only controls the DVD not the amp. However, if you really want to do that just teach the amp volume commands to each device and map those to the volume buttons in each Device mode.

3 - hit the Devices button twice.