Mapping the Source of the Attack

If this is your first time here, I recommend starting from the conclusion page.

As it seems that we're reaching an agreement about the UMLACA's range, and we have multiple independent indications of the rocket azimuths, we can now make a reasonable location estimate for the chemical attacks' launch site.

I prepared an area that roughly matches the calculated azimuths and falls within 2.0 to 3.2 km of the farthest impact sites (which also happen to be the ones for which we have an azimuth). 

Here it is:

And zoomed out: 

See the area in an interactive map.

It is interesting to note that the 12 impact sites seem to form an arc around the southern part of this area, which may indicate a series of launches made from the same point at different directions.

By the way, does anyone know who geolocated the other 10 impact sites? I copied it from the HRW report and saw it also in another map. I currently don't use them for the estimate, but would be helpful to know.
Update: In a comment, 'CE' referred me to footnote 16 in the HRW report indicating the site locations were collected from local activists via skype, and in some cases were based on GPS readings.

At this point, I would like to ask your help in gathering information about this area:

1. Who controls it? How tight is that control?
2. Are the residential areas in it populated or deserted?
3. Any other interesting events happened there during the war? 
4. It would be especially interesting if anyone could think of a way to contact residents of the buildings surrounding the area. They couldn't have missed the sound of 12 UMLACA launches, and must have valuable information or perhaps even a video.

Findings so far:
From the discussion here, I got this video published 3 days after the chemical attacks showing a rocket launched from Qadoum (I identified the minaret in the video to belong to Ghoufran Mosque). The launch is from the Special Forces HQ, which is 1.5 km northwest of the center of our suspected area. 
After examining the video frame by frame I could not determine if this is an UMLACA. Some frames seem to show an oversized payload and others do not.
The discussion provides reliable evidence that the area has been deserted and outside regime control for a long time, and indeed on the same day another video was published showing an attack on the area attributed in the title to "Assad's Gangs".