Does someone have links to literature on whether inequality causes crime?

There are links all over the place to the effect that the correlation between inequality and violent crime is well attested. There is a lot of quibbling about what kind of inequality correlates with what kind of crime, but the basic link seems sound.

On average, are more dollars stolen by rich criminals, or by poor criminals?

Rich, but does that matter? I'm not arguing that poverty causes crime, rather that inequality does. Whoever is a beneficiary of the inequality tries to maintain it, while whoever is a victim of it tries to correct it. If the inequality is modest and proportioned to merit, we can expect that both will remain within the law in their efforts; if the inequality is disproportionate, both will have an incentive to resort to extraordinary (and possibly illicit) measures.

I'm not denying the existence of middle class crime, but it's clear that inequality provides lots and lots of opportunity for crime; the greater the inequality, the more the opportunity.

In Mexico today, the body count in the drug wars

Yup, drugs supplied by poor countries to rich countries: inequality in law enforcement (which comes down to economic inequality) amplifying existing economic inequality.