Figure 2 is quite important. It demonstrates that the economic benefits of immigration do not only flow to the wealthy. Although scholars disagree about the distributional effect of immigration, it's quite clear that most native-born people benefit from it.
Figure 2.
You make a lot of good points but what this chart really says is economists don't have any reliable way of estimating this - which is unsurprising given the complexity of the inputs. One estimate would have a minor net lowering effect on HS graduates or less, the other would have a minor net benefit.
