Child benefit/tax credits/DLA/mobility

Hi all
I have shared residence of my two children of 10 and 11, my 11yo is registered disabled and receives high rate DLA and high rate mobility care component. I am in receipt of carers allowance of £45pw.
In february i applied to the DWP for his child benefit. On Tuesday this week, i received a letter from them stating that it had been awarded to me and backdated, leaving my stbx the child benefit for our younger son. I then contacted the tax credit dept and was told that as I have him marginally less than her, I wasnt entitled to the tax credits for him. I then contacted the DLA/mobility section to find out if, as i now receive his child benefit, would i be entitled to his DLA and mobility. After explaining the situation to them re the shared residence they said they would have to look into it. I have been told by friends that if you receive the child benefit it can open doors up for other benefits. Does anyone know the rules re the cb''s, tax credits, DLA/mobility?
So to summarize: two children (one disabled), me - cb for eldest
her - cb for youngest, child/working tax credits for both, DLA high rate for eldest, Mobility high rate for eldest.
any advice would be appreciated guys

Carers allowance is £58 45 per week.DLA and mobility are not separate Benefits- DLA has two components - care and mobility - Child benefit does not affect DLA as adults claim DLA also - what other benefits were you referring too? Your best option is to google the DWP website for the benefits you need information on.

i get £58.45pw in carers allowance, £45.15 in income support, and £20.30 chils benefit for my eldest. My ex receives his mobility component of £54.04pw and care component of £77.45pw and his tax credit disabled child element of £79.61pw.
As my ex will not willingly share the DLA money etc with me, I would love to know if I am entitled to ask for it either from her or from the DWP, or whether it can be split, as I now receive his child benefit?

To claim Carers allowance you have to be looking after the disabled person more than 35 hours per week- however if your ex is working she cannot claim this is she earns more than £100 per week.The DLA cannot be split- I would imagine you could appeal but as the Tax Credits are paid to her I am unsure how successful this would be

thank you for your info Linda