Well, there's always "Sam Hall."

Also a song Hoyt Axton sang called "Water For My Horses."   IIRC, both those songs are sung from the unrepenting perspective of a convicted murder.

(I do think that it may be easier in a novel than in a song to make it clear that the narrative is from the perspective of someone other than the author.   Maybe because the song is sung more often than the novel is read aloud.)

Bobert's got a that "there ain't much that can't be written about but there are a few topics that will sho nuff sink the song. Like:

...8. Songs about your late wife named "Honey" (think Bobby Goldsboro here)(makes one reconsider one's stand on capital punishement...)
LOL

Not sure if I fully agree with some of your others, though, Bobert.

"...
3. Songs in praise of the Iraq War..."   
Tell that to Toby Keith.

" ... 4. Songs about having sex with yer grannie or mom..."
Well, how 'bout that Scots song that goes
"Oh, ye canny shtoop yer grannie on a bus ..." ?

" ... 6. Songs about plots to commit crimes..."
Hmm... I think it depends on the crime.

The Dixie Chicks' song "Goodbye, Earl" and Martina McBride's song "Independence Day" are both about "crimes" (already committed), but crimes where the public is likely to empathize with the "perp."

And, of course, trad, folk song is replete with songs sung from the viewpoint of murderers of one sort or another.

Genie