Condensation is definitely a concern in colder weather. If you create a thermal break that isn't properly sealed against air leakage, warm air from the house will seep behind the walls, bringing lots and lots of moisture with it. Meanwhile the bricks, which are now insulated, are going to be very very cold, and when warm air gets cold it lets go of its moisture - and thus we get condensation.
That condensation would then get trapped inside the walls - and long before you have a problem with brick deterioration you're going to have mold issues that lead to health issues.
The best thing to do to prevent this is to insulate with a substance that also serves as a vapor barrier, which will prevent any air (and thus any moisture) from leaking into the closed cavity. The best product for this IMO is spray foam insulation, because it fills in all the nooks and crannies and IS the vapor barrier.
Alternatively, you could use fiberglass and cover it over with plastic to form a vapor barrier, and this can work IF you properly seal it all the way around the edges, seams and any holes that occur.
Either approach, however, is going to require you to sacrifice living space, as for a proper thermal break you're going to probably want at least 4" of insulation.
Now - with regard to insulating your spare rooms. Don't insulate your interior walls. Put proper insulation in the external walls of those rooms, so that they don't lose heat to the outside. Yes you will be heating them, but if they're properly insulated they're not going to cost much to heat and there are numerous other concerns with turning an inside room into a "cold" room - it's a finished space, after all, and you don't want to risk damaging that by letting it be freezing cold in there.
First I don't totally disagree with Tyler but his answer is a bit ridiculous. Only a concrete salesman would tell you to repour your foundation due to hairline cracks in drywall. Maybe the issue has something to do with the foundation shifting seasonally.
But all houses move a little throughout weather changes - humidity and temp. It is virtually impossible to ever create a house that will never have any cracks in the drywall unless you do everything perfectly and use only the best materials and keep the house climate controlled all the time. For 99% of the population adding on 20-40%+ more costs is not worth a few very minor cracks in their drywall.
So what can you do:
Take pictures and inspect the attic. You partly did this - not well because the pictures I see have insulation over the beams. If there is anything pulling apart you should be worried about the structure. If you start seeing trusses pulling (I have seen this) or gaps then you have a bigger problem - still not one that warrants a foundation repour. The fact is there might be a truss or beam that is not supported well or simply a cut that is 1/4" short on one side. A lot of times you can see cross beams in your ceiling drywall. This could be an issue with it moving or could just be old drywall or poorly installed drywall. We would need much much better pictures to piece this together.
Quit researching your dirt. Your house is already built, you live in it, why would you focus on something that you can't change? Your house has been up for 13 years and you have hairline drywall cracks. Did your builders do the job "right"? Who knows. Did they do a good enough job? Looks like it.
I am sure part of your problem is the temp/humidity variance between the different sides of your drywall. It is not a coincidence that the cracks came back as the nights neared freezing. Add more insulation, add better insulation, keep your home at a more consistent temp/humidity. It is also not a coincidence that this is happening on your second floor. Homes with real foundation issues have cracks everywhere including basement walls.
If I had to plop down money and bet why you keep getting these cracks I would bet it was simply due to the drywall installation. These are the cracks that you get when you don't float the outside of your ceilings. If everything is screwed in all the way through and wood is expanding and contracting at a greater rate than the drywall this will happen. I have answered how to float ceiling drywall before. I can tell you that this is your biggest problem - $50 drywall install. The company that came in basically redid the exact same thing as the original - did you expect different results. Did they think about cutting both pieces of drywall out and having one piece over that sensitive area? Did they think about using a different material? Nope just blame it on someone else and someone else that did something 13 years ago. I would laugh if contractors came back on a warranty and said that its your truss - so when they took your money they didn't need to investigate but when you take their time they do? I wouldn't believe anything they said period.
Second biggest issue is covering the drywall. When you have hairline cracks that pop up in the same places and you use drywall mud and sand/paint... well I can say that you should expect the same crack 98% of the time to show within 2 years. First get some mesh drywall tape. For a nasty crack I might use 2-3 pieces of tape layered slight different. Then you need to use plaster or spackle or at least something more flexible than your basic drywall mud.
Best Answer
I'm afraid the age of the house can not be blamed for the drywall seams being noticeable. Dry wall seams, when completed properly, should be invisible even under close scrutiny.
It sounds as if only 1 or 2 coats of joint compound was applied. The solution is to apply more compound in wider passes to ease the compound to the surrounding wall (Feathering). 1 or 2 more coats should blend it enough to be unnoticeable.