Hmmmm…..

1) I'd go the Dexter route. Other serial killers, rapists, drug dealers that sell to kids, if I can get proof that someone honestly deserves to die, I'd kill them.

2) Every serial has an M.O. I'd go with faking accidents, or copying a gang's methods, depending on the victim.

3) Hmm… hard one. I'd probably go with yes, but not something that could tie the death to me. Probably articles about their deaths. Highlight the important details one color, and highlight indicators of journalistic bias another. They would be hidden in with other, similar articles, to disguise them.

4) Ideally I wouldn't be known, but if I was I'd be the Good Samaritan killer- I'd be limiting myself to only killing bad guys, so I'd see myself as a good samaritan

5) Actually, as to the above, I wouldn't evolve to fully accidents or false flag killings right away. My first few, perhaps dozen, kills would get me labled the Good Samaritan killer, but I would seem to vanish eventually, mastering hiding my kills as the work of others, or plain accidents. Then, I could carry out my work in peace.