Would explain the fingers up the nose shot. Most people working in TV take coke. He is probably trying to exonerate himself. She has lost weight very quickly several times which is classic. I am not sure why people are shocked Is it cos she makes nice cakes?
I don't think he was looking for evidence just highlighting I know when my brother was doing drugs and we were begging him to stop I would sometimes grab him and rollup his sleeves etc and say Look wtf are you doing etc. Not nice but we were sooo frustrated at times with all the deception. I think its an everyman for himself situation. He is trying to label her a coke fiend to counter the abusive dh tag. truly awful all round.
I think taking drugs with her kids is the saddest thing. She has had a terrible past with family and bereavement and an emotionally absent mother. I can imagine that would blur the parenting boundaries a lot.