KYLO = sKYwalker soLO
Ren is the name of Knights of Ren so he didn't choose it. It just happens to be similar to Ben.
kYlo REn also contains letters that make REY.
Good catch on psychopaths and self-preservation. KR has ZERO sense of self-preservation. And not just this fight. dropping the droid for the girl is lack of it. Self-preservation = covering one's ass at all times. KR doesn't do any of it.