Greetings,
A very do-able TV reception plot. You have a mix of green (good strength) and yellow (moderate signal strength). Further a positive you have is that the stations you seek aren't terribly off axis of one another. Thirty-five degrees or so is your arc. There are antennas on the market that will accomidate this no problems.
Attic install is not suggested. This is due to the unpredictable environments that attics cause. They weaken signals 20% or greater, induce multipath and bring the antenna much closer to household electrical interference. Of additional importance to you, WLOS (ABC) at 19 db signal strength is below the threshold of common attic reception. Generally anything below about 25db in signal strength simply cannot penetrate your roof with enough signal strength for reliable reception. Thus, if you want an attic install, you have to go in with the notion that WLOS will be in the "luck" category. If WLOS is a desired catch, then it is highly suggested you mount outdoors just on the basis of WLOS' signal strength.
Unfortunately, a smaller antenna that'll mount to the dish J-style bracket is isn't an option here. If you had all green signals with line of sight conditions, then yes, you could do that. What graduates you to a larger antenna is two things: 1) WLOS at 19db signal strength by nature means a larger higher gain antenna to work the weak signal is needed and 2) WLOS 1-edge condition at 56 miles.
So, you have a choice at this point. A larger antenna is required. Any attempt at the smaller ANT751 or HBU11 type antenna will likely get you green signals. WLOS though has a greater chance of not being reliably off this type of antenna. Those antennas are designed for suburban and line of sight conditions - to which you are neither.
If I were installing with your criteria. I would mount off the roof with a clear and unobstructed view to magnetic 345 a Antennacraft HBU33.
http://www.antennacraft.net/pdfs/HBU33_.pdf
If you have trees surrounding your property, that becomes a wild card. Trees can reduce signal strength and reflect signal away from your antenna. The result is unreliable reception.
Best of luck.