consider a taillight that is daylight visible, or nearly so.
A Dinotte, or a Magicshine, or something like that. Pack the lumens. I have found that the Magicshine taillight I added seems to be the single most important component of getting cars to give me space at night.
Also, as much reflective tape as possible. I have a very large area of red on the backs of both of my fenders, and bits around my chainstays. I have bits of white on my fork legs and the fronts of my brake levers. I also have both red and white reflective tape all over my helmet, front, back, and sides. My pack, an Osprey Talon, has reflective bits on it, too, but I like that reflective triangle. Right now, I toss a blackburn blinkie on my pack, but I'm not a fan of how it hangs from the pack.
In addition to what you are doing, how about describing the route you ride? You say busy city streets but that can be a lot of things. how many lanes? speed limits? are there shoulders or wide lanes? My route is about the same distance and the way I drive is down busy streets more than 3/4 of the way there. however I take a different route when I ride. speed limits are lower (about 2 miles are neighborhood streets where I pass a school and a hospital with 20mph zones), so traffic is lighter, and incidentally, the lanes are much wider even though there's no paint on the roads there. The better route adds about half a mile, but it turns out to be faster because there are fewer lights and stop signs.