Hi Upekkha100,
1) The meaning of anatta as “does not hold any truth” seems a bit confusing at the face of it. But in some cases it may make sense. It may depend on the context. For example if we look at scientific or philosophical theories we may be able to see that they may not hold any ultimate truth.
2) When it is said that anatta becomes completely true for an arahanth, I think it means that only when a person reaches the arahanth stage does one fully comprehend anatta.
4) Yes, this is another way of looking at it, and I think this has been explained by Lal in some of his posts as well. I guess when one looks at things from the point of “yan dukkan thadanatta”, if one brings dukka then it is anatta, we can come to the understanding that if something doesn’t bring us happiness then there is no permanent refuge or protection in it.