I must have missed it too, damn eye blinks moments.
When Ashleigh talked about deciding who to put up Mark mentioned Ash's name before she had a chance to. He then a minute later went to say it would go down with Helen and Ash if Ash was up and them taking it out on him but he could handle it. So no he didn't fight for Ash. Nothing there to indicate he did.
As for new information fed into the house and acting shocked about Zoe, he's been on the reality circuit too. I find Zoe a bit annoying but she doesn't play up to the camera's nowhere near the amount that Mark does, everything is put on for the audience. If he wants to play dirty, the new hm's should expose him for what he is, since he is happy to turn the whole house against them and pass the stick from himself to Ashleigh and Chris.
The little orange
tanned munchkin uses the term smiling assassin and is the perfect example in my opinion.