- Test in the context of Skill (Say, for example, testing the swordfighting talent of someone.)
- Test in the context of Fantasy (Checking a historical truth against historical myth.)
- Test in the context of Desire (Testing how deeply someone wants something [coming-of-age, maybe?])
- Test in the context of Confidence (A character, being required to verify their claims of certainty.)
I'm not sure which of these are in your book, but those four are all Test. Yet, they each look a little bit different. The difference can be made more extreme if you go up a step to Types/Concerns or two steps to Classes/Domains.
I think this is part of what the idea of "I", "You", "We", and "They" are trying to get at. Since, per Dramatica, a story is a mind exploring an inequity, that mind, I, would take one stance on the problem or dissonance. (Maybe I'm dealing with bullies in some fashion, hiding from them, avoiding them, etc.) [Physics]
From that standpoint, I would pick a singular, similar, person that seems to be solving a similar problem or dealing with a similar dissonance, and attempt to understand how it looks from their side. In other words, what this problem or dissonance looks like to You... (Someone else dealing with distant parents who don't seem to care about this person. The problem is similar to mine, as illustrated above, but it's different. How does he or she deal with it, and does it work or not? Why does it look so similar, and can this one person's approach work for me?) [Psychology]
In addition to working with this singular, similar look, the same mind might also see how a group of people, of which the mind may or may not be a part of, is dealing with another problem, but one that looks similar. (Perhaps the country, They, where I live is in a cold war of sorts, staring down another. I'm a part of the country, but the problem is too far removed for me to do much about it, because I'm a lowly farmer. However, that doesn't mean I'm not watching the news, trying to keep tabs on what's going on "out there".) [Mind or Universe]
Finally, since I don't have a storyform for this, I actually don't know what the We perspective would be to round out this brief outline. However, it is a relationship, and the question becomes how are We as friends, lovers, enemies, strangers, or something else, dealing with our own issues, issues separate from the world, issues separate from the bullies I'm dealing with, and separate from the parental issues You're dealing with. [Mind or Universe]
As to the IC, I think @mlucas answered it fairly well. It turns out that's actually the hardest throughline for me, as I almost always end up trying to treat that throughline like another MC. In order to get it right, I had to force myself to make sure I was "taking a step back" from there by using words like "seems to" and "appears to be" and such, even though I actually know exactly what is happening.
An important part of all of this, however, is to notice that there may very well be scenes with just that character with his parents. Scenes of which the Main Character is completely unaware, but the audience gets to see. Without those scenes, it would be difficult to actually show the problem or dissonance the Influence Character is dealing with. However, that doesn't mean that we will fully and completely "feel with" the Influence Character. We'll probably get very close to it, though. Still, there might be some hidden information; we might only be able to guess at the thoughts of that character, though we'd probably be close to the mark with that guess.