The idea that one cannot derive an "ought" from an "is" is so often asserted as a settled fact and so rarely actually argued by means other than historical difficulty or personal incredulity. I'd prefer it be stated without the chaotic inversion, if at all — not "one cannot derive an 'ought' from an 'is'", but "I don't know how to derive an 'ought' from an 'is'". In any case, have you read the metaethics sequence? A lot of people seem to disagree, but I found that it mostly resolved/dissolved this problem to my satisfaction (you know, that wonderful feeling when you can look back upon your past self's thoughts on the matter and find them so confused and foreign that you can barely even empathize with the state of mind that generated them anymore).

(Also, I find your claim that wanting is not a naturalistic property baffling, and your argument for that also seems to boil down to personal incredulity (I don't know how to explain wanting in reductive naturalistic terms -> it's impossible).)