Single parents should be exempt and anyone with a disabled child.
I know a few women who are SAHMs because their child has a disability, my next door neighbour is one, she cannot get a childminder or after school/holiday care for her child so is forced to be a SAHM, her husband is a HRT so she loses her CB. I don't know what else she is losing through the other cuts.
I think 80K would have been much fairer or reduce it to 2 children only, a standard payment, much easier to administer, or group it in with CTC.
Vinegar - I mentioned how much it would be before tax as yes this is how much my DH will have to earn to make up for the loss (fat chance), we will certainly feel the loss and will cut back accordingly. But I cannot moan as I am a privileged SAHM who chose to have 4 children, I should only be allowed 2 and be back at work earning income tax for the government as that's the only use they see people having, if you cannot work and pay tax, you are a parasitic drain according to the Tories, unless you are a politician with an expense account or a multimillion pound business then you don't need to pay tax 
It's only the start next it will be clawed back to 45K, then 30K then lost altogether