Legally what's she entitled to as regards support over & above childs maintenence?

It is a complex issue. She should be entitled to half of everything including money that he is currently entitled to in the future. If he is offering more than half, then that should be balanced out in the future. He likely would only pay for 1/2 of the child's care including housing. If she is capable of working, which she has in the past, then it would be expected that she may have to do that again. She is entitled (perhaps) to half of his pension.