Once again, you have produced an essay of astounding length and intricacy.
While I can't possibly answer to all the nuances of your argument, I agree that our social structure is based on scarcity. We are quickly approaching a post-scarcity society - through labor replacements, more efficient technologies and the potential for superstructures such as solar power satellites, space elevators and so on.
I don't think that decisions about the social aspects of this work lie in the hands of the roboticists, though they probably understand more than anyone the long term potential for their machines to replace all labour. I think that those decisions lie with the general populance.
I for one would love the transition to a gift economy (or perhaps something more like the Star Trek economy) - our capitalistic society has worked well for us so far, but soon the few things that humans can UNIQUELY do will have to be encouraged. Capitalistic mechanisms are very good at keeping the rich rich, like you say. Much better to free people from the need to get enough food and shelter to survive and then to capture the public imagination with mega projects that really do require human involvement.
My main point is that we shouldn't fear technology. I agree with the thesis of your argument which seems to be that massive change is coming, so we better embrace it and prepare for it.
It really is just a matter of time until all the unskilled labor is replaced. I hope at this point that every human whose job is threatened is capable of finding a calling that is uniquely human.