1. good!
2. rtabmap-console is for loop closure detection only, not for RGB-D mapping. You must process the database with rtabmap application using the
database as source. The problem when using the rtabmap-recorder alone is that you can't have a feedback while recording if the odometry can be computed (like using the recorder from from the EDIT menu of rtabmap). So if the recorded images are poor in features, you will only know it when replaying it in rtabmap and if the odometry get lost.
3. You could run rtabmap standalone in localization mode, but you will not get any output (readable from another app at the same time) like the topics sent by the rtabmap node in ROS. You may use RTAB-Map library in your C++ code though.
cheers