I don't have time for all of those, so I'll just do one.
The genetics/crime issue is an incredibly difficult to study one, due to fears of eugenics. XYY males are a perfect example of this: in the 1970s, there was a huge controversy over a study which had indicated that 2% of the US prison system was XYY, while only 0.05% of the US population as a whole was. There were cases argued in court that the client wasn't guilty because of their genes, it was called the "criminal genotype", etc. Public pressure on this front effectively halted all future research on the subject. There have been some minor studies since then, but nothing that could remotely be called conclusive. There also are other "causation" issues. Since XXY children look different, there is the risk of an increase in being teased as a child, which may or may not contribute to violent behavior. While its causes are still not completely known, there may well be a link to alcoholism or drug use in the father - which itself may increase the likelyhood of the children developing violent behavior. Etc.
That said, there are quite a few genetic conditions that affect behavior, so it only seems likely that a predisposition to violence may also exist. Examples of genetic conditions that affect behavior are Lesch-Nyhan syndrome, schizophrenia, Tourette's syndrome, and even the rare syndrome (confined to a single family! They can actually trace back the mutation) called MAOA (a mutation in the production of monoamine oxidase A, which is tied to impulsive violent behavior).
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