Am I approaching samadhi properly?
Yes, concentrate on the sensation of the breath and nothing else. 

This will develop samadhi &amp; but also vipassana because the breath is impermanent. 

While samadhi is developed, seeing clearly the impermanence (appearance, disappearance, appearance, disappearance) of each breath is vipassana. 

Thus the primary goal is to develop samadhi but a side effect can be vipassana.