Tim. Reading your thread this probably will not be much use but my daughter, Rafaela was abducted to Brazil just over a year ago by my Brazilian wife. (I received some very informative and supportive emails from several of you at that time.) My wife changes her statements about returning regularly. The Brazilian Consulate in London refused a travel authorization for Rafaela because it had her British passport number on it. They said that she must now have a Brazilian passport to travel (although my wife illegally took her into Brazil on her British passport!).
I visited them in Brazil a few weeks ago when my wife was saying that she would return. During my visit we went to the Federal Police in Campinas who contradicted the Consulate. They said that there was a new ruling that states that dual nationality children can travel on their non-Brazilian passport.
Here is the explanation and reference written by my wife for the Consulate:
A Polícia Federal de Campinas, do setor de Passaportes informou que a IN 72/2013, permite que passageiros com dupla cidadania, viagem com seu passaporte estrangeiro. Ele não imprimiu porque como é muito novo, provavelmente ainda não foi postado na internet. Porém, os Policiais Federais nos aeroportos internacionais do Brasil, devem estar a par desta novidade. Ele orientou me a mostrar o nro da IN (72/2013) que eles saberão do que se trata, no caso de algum problema para embarcar minha filha com o passaporte Inglês dela. I have not had a chance to test this as my wife has gone backwards and is now not communicating with me (a typical pattern when she changes her mind).
I can see that your case is more complex but if you have not come across this before, perhaps it is of interest.
It is great when there is a chink of light appearing sometimes and my thoughts and hopes are with you.
Tim Pascoe