The study your citing doesn't say what you are claiming it does.
> It is also important to recognize that the five external costs calculated in this analysis do not encompass all possible external costs associated with vehicle ownership and use. For example, noise pollution imposes significant costs.
Not only does it not even attempt to put a total cost per mile - which I read as the main reason why you cited it. It directly contradicts you when you say "Noise is also a rounding error".
It specifically excludes some of the biggest costs
> Based on his review of the transport-cost literature, Litman (2002) believes that the largest external costs of automobile ownership and use relate to land use impacts [...] However, these costs are, to a large extent, indirect. In other words, they are a result of auto-oriented travel patterns and will not vary much by vehicle type, make and model. Thus, they are not examined here.
Another quote to make it extra clear that this study really doesn't say what you are claiming it does
> Many other external costs associated with driving exist, and many of these have been characterized at an aggregate scale, rather than by make and model. For instance, [...] disposal costs. Water contamination [...]. However, like the noise and land use costs described above, these other costs are difficult to distinguish by make and model. Thus, they are not covered here
A quote explaining what the study is about
> While certain studies have analyzed other types of external cost, beyond the five quantified here, these studies have been aggregate in nature, focusing on passenger vehicles as a whole, or cars versus light-duty trucks. In contrast, this work looks at likely variations across specific makes and models.