But if we adopt the conventional practice of translating "lo tirtzoch" as "don't murder", and further adopt the conventional practice of not labeling killings we're morally OK with as "murder", then I squeak by here as well...

I think the general idea is that by "murder" the concept of 'do not kill people without it being prescribed by the law' is meant -- with the rest of Mosaic law indicating in which cases it was okay to kill people nonetheless.

So killing insects doesn't count (because they're not people), nor being a state executioner counts (because it's prescribed by the law).