DK files are drum patterns. You have to load these thru the program. In RB it is 'Edit-fill track with drum pattern' and then you see a list of the available patterns. These are drum patterns of a few bars in nature and will be copied/pasted repeatedly to fill the track. You can easily make your own DK files, by the way.

If you are in BiaB then you can only have one synth, so which synth are you listening through? The soundcard, DXi or the Roland?

In RB you can use all three at the same time, but in BiaB it is only one MIDI port at a time. It could be that you are using a different synth than expected, or BiaB messages meant for one synth are making their way to another. For instance, sending a message meant for the software GM synth that gets received by the Roland synth (when not in GM mode) would have 'unexpected results.'
So let us know exactly how you are set up for MIDI presently and what you would like to be able to do. It will easier to explain than for us to try to figure out your 6 table theory and then adjust. I didn't understand that part of your question at all.

I do not work here, but the benefits are still awesome
Make your sound your own!