That's mostly right, as far as the currently known bloodlines go. One thing to note, however, is that the Ruiner's bloodline also appears to be what grants the ability to consume and absorb other bloodlines.

I can't say too much about this since it involves spoilers, but there are some strong hints in the past few dozen chapters. Specifically, remember that Arran spent quite a bit of time in the shadow world, with shadow essence not just permeating his body but also nourishing him. Next, consider what happened to his control of (shadow) magic after that, what the state of his body was when he emerged, and whether the rate of his strength increases has changed since he returned to his previous peak. That should give you some idea of which way he currently leans in the magical/natural balance. Of course, all of this also points toward an interesting question: what would happen if someone's magical or natural affinity was taken to the extreme?

Yeah, I know. Clearly, my writing speed hasn't quite recovered yet. ETA for the next chapter: next Sunday.