David, Everything that you are showing here is “normal” to almost every house in that neighborhood, built under these specifications, viewed under these weather conditions.
Heat around a chimney is because there is a gap left at the connection to the building. Air in the attic is always warmer than outdoors (winter and summer). This space is supposed to be there.
Areas around fireplace walls always have gaps. What it costs to access these areas is greater than the cost of 10 yrs of efficiency losses. I have them in my house and didn’t fix them till I remodeled the fireplace years later.
Fiberglass batt insulation always leaks when not properly installed (eventually you will see what everyone has been missing all these years before IR).
There is always air leaks above the exterior wall headers because there is supposed to be ventilation there (plus insulation in the shared space).
You are going to have to learn to “see” again! 
This is what has been talked about in the past: “You must know what your pointing the camera at to utilize IR on it.”. In time you will learn more than you ever knew before.
When I went to Level II in Boston, I stopped by a commercial building I had insulated as a kid 30 years earlier and asked the owner if I could scan it. I built it (not knowing what I now know) and wanted to see how what I did worked.
When I went to Building Science in Boston, I sat down with Scott Wood at lunch and did the same thing your doing here on a house I inspected that was in a law suit (which I used IR on before I had any training). I luckily was spot on. I had not committed my thermal findings until I completed my training…
Keep it up. IR is not point and shoot. Also Thermal Inspections go way further than most HI’s Inspection Standard. You don’t just see something and call it out (after coming here getting an onslaught of guesses). You must further investigate (especially now at your current level) what is causing the anomaly your looking at. Determine if what your looking at is in fact a “Significant Deficiency” to be reported.
There is an air gap around the chimney.
There are spaces at all fiberglass insulation splices.
Wall fiberglass that is not secured to the Sheetrock gets an air gap that causes convection losses and renders that insulation batt useless, even though it is in fact there.
Also, do not depend on the moisture meter. It lies. Even when there is measurable moisture, it my not be anything more than an air leak condensing.
Upload your scans to Drop Box or something. I talk with you about stuff over the phone. Your a good conscientious Inspector and your going to make a good Thermographer. I’d be happy to help.
