My apologies that your question has not been answered in a timely manner. It seems to have somehow fallen between the cracks.
I’d like to take the opportunity to answer all you’re questions point by point.
You ask if the Rav position is that most grape juice is cooked? That is correct but absolutely does NOT mean that All in fact are. Moreover there may be ample time to touch the juice prior to its cooking process. Therefore plainly put all grape juice needs supervision or the precise knowledge of the process!
As to nullifying in 6, you are incorrect that it suffices for yayin nesach. It nullifies only what we term as stam yanam, which is the status of our wines today. (Minus those used in churches and the like which in fact are true yayin nesach)
Additionally it can only be nullified in 6 times of another liquid not a solid.
Regarding your last statement, you are most definitely correct. This is the only site for Rulings exclusively by Rav Yitzchak Abadi, and any question that is not found in our archives needs to be asked again.