So, from what I can tell, your controller is producing pretty accurate measurements, much better than spec, and you've just been misinterpreting what they should show.
First, you said USB, which is 5 V. But the load terminals are ~13 V. So I assume you have a 12V-USB converter in there. A perfectly efficient converter would produce 5 V @ .55 A from 13 V @ .21 A. Your chart shows an increase of about that, so the relative change looks reasonable.
Something similar would apply to the Raspi. They don't run on 13 V, either. You said you measured about .330 A. If that's the 5V draw, then the 13 V draw would be about .13 A (= 5V*.33A / 13V), which is pretty close to what your chart shows before you added the new load.
(looking back, you did mention DROK USB way back on page 1. When you've been referring to "DROK," I've been assuming you're using one of their voltage/current monitors directly on the load line)
