I think that the Rob / Helen relationship is brilliantly done. As a previous poster said the actor who plays Rob makes everything sound so menacing. It's partly the way he pauses when he finds someone else at the house with Helen. He sort of says "Ah." Then long uncomfortable pause for Helen to feel that she's done the wrong thing, then something like "I didn't know your mum / Tom / Emma was coming over." The unspoken implication being that Helen either shouldn't have people over or needs to ask his permission. But of course he never actually says that because she might realise he's being unreasonable, he just manages to make her (and I suspect Pat) feel uncomfortable so that they are less likely to do it again, without Helen ever really asking herself why.
He speaks in a curiously even tone as though he's repressing anger which I find quite scary just listening to it. He manages to give the impression that he could totally lose control and become violent. I can really understand why Helen doesn't want to "upset" him. She doesn't actually seem scared of him yet though. I wonder if that will come?
The other thing he does, which I think is brilliantly written, is when he knows he's got his own way, eg over the shop in the last episode he then says "Of course if you REALLY want to / feel you need to do whatever, then you should." By that point he knows that Helen's going to do as he says but by saying that Helen falsely remembers it as being her own choice to give up work / go hunting / stop inviting Emma round / say Rob doesn't need to take a DNA test.
I think Pat is being very wise not directly confronting Rob. If she does Helen will take Rob's side and Rob will succeed in cutting Helen off from another person. Pat (and Tom?) need to try and get Helen, very gently, to the point where she is willing to stand up to Rob herself.