I am only answeing the next two questions here but I am terrible at planning my time and my eyes are going a little heavy. However I have read again all the questions and I think I can see better the unity in your thoughts and that it will make answering easier.
17. Generally yes. Where I am still questioning is how we arrive from where we are, with sex being commodified harming mostly everyone whether we partake in it or not, into such a consent based society. But my own lack of imagination is no limitation for what is possible.
18. Yes. Essentially all societies have created some form of elite classes with more rights or privileges than others. The sources for this power have varied immensely but you can notice them if you observe it well. The main exceptions have been small communes. Those are limited by Dunbar as they need strong cohesion and social bonds in which norms can be universal among the membership. And they still often degenerate into creating elite classes over time. Especially as they grow larger. This has been attested in history. Back to the question, recognizing the rights of children as worthy humans, one of which is sexual expression freely and openly, definitely would alter power structures in society and would either require to be established or lead after it becomes true, or both, broader and deeper social changes. To a significant degree this is a reason why I'm at a loss at how to move from A to B. It is a Gordian knot.