Hi Artemis, and welcome!! Wow you sure ask a lot of good questions! I can't answer them all, but others will eventually help out with this.
I'm of the "absolutely no sugar and no refined flour" school of thought. I eat as little of both as what is humanly possible. Not because I crave either (anymore), but because it is very hard to buy food in today's world that does NOT contain either of those. In this scenario, all one can do is go with the lesser evil, and use common sense + moderation.
In the process of making bread, the bakers use some kind of sugar to feed the yeast so that a lighter and more "airy" bread is produced. This has to be mentioned on the ingredients label, but fortunately the yeast do eat a great deal of it before the baking process. However, some bread manufacturers add
extra sugar to the recipe (more than the yeast can consume) to lighten the flavor. Avoid any whole wheat bread that has extra sugars added (honey, molasses, high fructose corn syrup, etc).
Barley is a grain. I use it in place of brown rice because it has almost
half the GI value! This is a quote I found online about "malted barely":
"Malted barley is a naturally processed form of barley. The grain is steeped in water and allowed to begin sprouting. This germination creates enzymes which are required to convert starch to fermentable sugar."
The enzymes in the malted barley feed the yeast. So this is legal and probably more so than bread made with sugar!
Sugar alcohols I know little about, only that they are slower to metabolize in the system (this is what makes them legal in
small quantities). Sugar alcohols do have a laxative effect in many people, so the "moderation" warning is well placed!
All in all, the best I can tell you is to prepare as many meals from fresh ingredients as possible. The food manufacturers are out to sabotage us with prepackaged foods that are high in sugar and refined carbohydrates. When I decided to use Sugar Busters as my "food mantra" I basically had to learn to cook all over again! I had relied for so long on "convenience foods". But I'm so glad I took that step! I feel so much better, and my doctor is well impressed with my new, healthier test results.

Sam