I watched this as I think KH is nearly always good, whether comedy or drama. I was confused to begin with as I didn't know it was meant to be darkly humerous!
I think you just have to buy into the idea the KH and her now dead husband had a realtionship where he did his work and she took little or no notice, or he deliberately told her very little. In fact the daughter seemed more aware.
And for the plot / humour have to believe that both KH and daughter have never been to the house, and he is thinking he is going to spend hours showing off all his gadgets.
There was another crime series (much more "serious") where the wife of a business man had no idea about what his work was and so on. So quite a usual plot device.
The inheritance tax thing is because he "gave" the house to his parents. (Presumably so it couldn't get seized as assests if he went / was going bankrupt.) But because he is now dead they will have to pay inheritance tax of some huge amount. They dont have that sort of money. So they will have to sell to pay the inheritance tax. She will not have a home (and yes where were they living before?) and they will nothave much to show for it. And their previous expeience of bankruptcy is making them very very concerned.
And much as I like that fact that some older stars have got parts, so disappointing that they are all playing such stereotypical roles.
I almost feel sorry for all of them, because obvioulsy what some writer and some producers thought was really new and cutting edge, is in many ways not that original.
And for me, which I hardly dare admit, I am actually thinking, on no I have seen KH do that little quirky thing before.
But even without knowing her back story, how anyone reacts to grieve is not going to be some stoical weeping wife.
And I will stick with it as know I want to know what the back story is. Because that is what it is really about. Everything that led to the point where he opened the door to the new house and they went in together for the first time.