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For example, how does ID account for the barrier between supposed Macro and Micro evolution?
ID doesn't necessarily assume such a barrier. For instance, an intelligent being could have designed and built the first protocell and planted it here on earth and the rest of life unfolded just as evolutionary theory suggests it did.
However, the big problem is that there is virtually no work being done to support Intelligent Design in the positive. Instead, it basically takes its strategy from creationism and tries to disprove evolution. What are the flagships of the ID movement? Irreducible complexity. The eye could not have evolved from simpler functional units, so therefore ... ID. etc, etc, you know the drill.
So the question becomes this, what criteria could we establish that could only be true of an intelligently designed universe? What could we know about the designer (assuming that this is indeed not a religious exercise that prescribes to know about a particular deity or creator) that we could confidently assert would be true about our universe that would be true if and only if it were designed by this unknown force?
I would say that on the surface ID has some appeal, but there is really no substance to it. It may as well be creationism, just with open ended parameters.
Can someone explain to me what predictions and explanations ID offers?
I think to some it offers a seemingly legitimate compromise between their religious belief and the overwhelming evidence produced by science. To me though, when it is presented as some unknown designer, it fails to provide any religious benefit and when it presents the science in such a way as to say "no point looking further than this because it was designed" it fails to provide any scientific benefit. So it just doesn't seem to provide any benefit.
Can someone more versed in ID theory speak to my points?
Again, ID doesn't necessarily have the barriers you indicate, but in general, it doesn't make useful predictions or provide useful explanations.
However, there was a member here who did a really good job of presenting some testable hypotheses related to intelligent design. You could read through them if you would like.
Revisiting the Type III secretion systemTowards a Hypothesis of Molecular DesignNature's Engines and EngineeringDeep Homology and Front-loading
HBD
Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca
"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.
Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.