I recognise the following from my family in the OP's situation:
Father who expresses his love for the wife by giving her what she wants unconditionally - family, money etc. He leaves the personal relations to her, and sees things from her perspective and backs up her all decisions, with an occasional bit of behind the scenes discussion, but basically this is her domain. She is now short of some grandchildren and he wants to get them back for her. Everything dances round her, she is the centre and this gets dysfunctional when you start involving other people, ie the children grow up into other people.
The obsession with a favoured person, opting out of the difficult problems of personal relationships and therefore not learning useful skills in that area could all be asd related.
I had a hell of a time with my mother, and when I eventually called her on her favouritism, it went tits up and she didn't ever admit to it. We ended up with a more distant cooled relationship as we both tried to avoid NC - there had been too much in previous generations on her side. A triumph of sorts, I guess. I feel very detached from my parents, and the love has been replaced with a sort of calm duty.
I would take heed of Meerka's advice and reply in a way that you are making (almost permanent) breathing space, without absolutely slamming the door.
I would agree that favouritism is not something that will change, no matter what you do. It is easier once you can take a philosophical approach from a distance.
I think it is important to nurture a balanced relationship with one's OH and there should be no opting out, or leaving it to the other because they are seen to be better at it as far a relationships with the children go. If one does it all and the other just backs them up blindly, you end up with just the input of one parent, when you could have had two, only you think you have two 
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