I'm only going to bother answering the last question, on the power of size. In short, lust can make you do things you'd never expect to do. For those with a size-fixation, that find it easy to lust after large penis, I don't see how the same thing wouldn't apply.
Edit 2:
Example:
I feel sickened by Shota but if the characters have massive cocks drawn on them, I could care less.

I personally find incest disgusting but that's simply because I have an extreme dislike for my brother at times. However, it's not disgusting enough for me to care about when someone posts it here. LPSG isn't serious bussiness.