These are good and deep questions. So deep, in fact, that I'm not sure what they mean! So even though I'll offer my 2 cents, what I say may be non-sensical.
Are scriptures in support of an idea any more than someone's understanding of scriptures in support of an idea?
I don't think you can separate Scriptures from our understanding of them. For example, if I told you "Lorem ipsum dolor sit amet", you wouldn't simply quote it in support of an idea -- because you don't know what it means.
Does one reason any less by citing scriptures?
There may be less reasoning going on when citing Scriptures because we usually cite Scripture when we think we know what it means. So Scripture can become sort of a "label" that carries with it some meaning that we don't have to reprocess every time we cite it. Kinda like if you meet a Republican and start talking politics. You don't have to cover the basic beliefs of a Republican because you know that label implies certain basics.
Do you agree that God's reasoning is "cover to cover", and man's reasoning is any portion thereof?
I don't know what that means?
Have the "plain faced" meaning of scriptures ever changed for you?
They probably have, although I don't remember any more. Even "plain faced" text can assume a new meaning after we've had more experience, learn more about the culture, learn more about what the rest of Scripture says about things, etc. It's the whole idea of maturing in the Word and being able to understand things more fully than we did when we were only drinking milk instead of eating meat.
Is it more important to have "scriptures in support of an idea" or sound reasoning in support of one's understanding of scriptures?
I think this is a false dichotomy. I think they're blocks that build on one another. So you must have sound reasoning in support of your understanding of Scripture, and then the Scripture can provide support of an idea. If your understanding of Scripture is wrong, then using it to support an idea will be invalid.
Does the sanctifying enlightenment/repentance process, through which Holy Spirit leads us into all truth, circumnavigate the very human reasoning process?
Certainly there are times when what we believe to be true may go against human reason. After all, God's ways are not our ways, and His thoughts are not our thoughts. I think, though, that going outside human reasoning should be the exception instead of the rule. We are told to love God with all our *mind*, too, so human reasoning, as tempered with the Holy Spirit's enlightenment, should typically play a role.
Does the process sanctification circumnavigate: human reasoning, language, literacy, instruction, polemics, observation or experimentation?
I think what I wrote above addresses this, too. But I would emphasize that the Word is the ultimate authority over other things (like experimentation). The Word is true, and if our experience doesn't line up with it, it probably means we're misunderstanding what Scripture means, what our experience means, or both.
If the word is proof, why is it tested?
Not sure what you mean by "tested", but you can test something in order to "prove" it out. For example, if you build a bridge under correct engineering principles to hold a 10-ton load, you could then "test" the bridge by putting a 10-ton load on it -- not to see if it will collapse, but rather to verify that it won't.
