I installed cable for Time Warner for several years. There is no good way to get an additional cable down that wall and have it inside the wall, especially with those short slats holding it to the concrete. As you noted, the roof line right there makes it downright impossible to drill a hole from above.
You do have a number of options though that may meet your needs:
You can use the existing cable to connect your antenna.
I would recommend you run a RG6 coax line from your antenna in the attic to where ever all of your cables terminates (You'll also need something like this). This may be in a central location in the house, or it may be on the outside of the house. Most likely its in a spot that's easier to get another cable to than that wall.
Once you have the antenna there, you can utilize a splitter to connect your antenna to as many outlets as you want to receive the signal. If its only one location, you can use a barrel connector. If you have more than 5 outlets, you should utilize a signal booster; and in general you should try and use good splitters. A good splitter will typically put 3.5 - 5 db's of resistance on a line.
You could run the additional line on the outside of your house
Drill up through the eve of your house being careful to ONLY go through one layer (You don't want to go all the way through one layer and then through the roof). Utilize a grommet to cover the hole, stuff a bunch of RG6 into the attic, and then use a coat hanger hook on a broom handle or something similar in the attic to pull the cable and connect it to your antenna.
On the outside wall you'd then utilize anchors and screws or tapcons with cable clips to hold cable ties to neatly run the cable down the exterior wall. You would then drill through the wall with a masonry bit, and preferably a hammer drill (You can rent them at Home Depot). Have your cable go down past the hole, and then do a loop back up and through the hole you drilled. This makes it so that water dripping down the coax does not go in the whole.
On the inside of your wall, cut a whole where your drill came through and use one of the low-voltage short drywall boxes to hold your outlet. You're now good to go.
You could run the wire on the outside of your interior wall
Home Depot / Lowes sells a number of channels for hiding a cable. Carefully drill a hole through your ceiling into the attic and stuff a bunch of cable up there, get it with a broom with a coat hanger and hook it to your antenna, etc.
On the inside you can hide the cable in one of the electrical channel things you can buy at Home Depot.
You could try to put two holes in your wall to get the wire in the attic
I don't recommend you do this, as its REALLY easy to mess up with as close as your drywall is to the cement block; but it can be done. This answer best answers your specific question, but I don't really recommend it.
Get one of those low-voltage, short boxes from Home Depot or Lowes and cut out a hole in your drywall about 1-2" below the top of your wall. Utilizing a drill at an angle, drill a hole upwards through the furring strip on the top of the wall. Be VERY careful to not go crazy, or you can drill through that strip AND through the roof. Once you've drilled through that, stuff a bunch of cable into the attic and hook it like I described before to get it to your antenna.
Then cut a second box directly below the first hole, again using the low voltage boxes. Stuff a bunch of cable down the high up whole and utilize a coat hanger / hands to try and pull it down the bottom part. You can also use fish tape, or fish rods; but I wouldn't necessarily buy them for one job.
Once you have them down; finish them as before. You can put a blank wall plate over the hole that is up high.
Hopefully these help. I'll try to add some links to what I'm talking about with the various steps to hopefully help.
I think the first solution is by far the best solution.
