Providing you will be the resident parent then yes your DH will be expected to pay maintenance. Chech out your CTC entitlements etc on www.entitledto.co.uk. Saw your other thread QE, sorry that things are like this for you at the moment.
It doesn't matter how much each parent earns, what matters is who gets the Child Benefit. They will be regarded as the resident parent and maintenance should be paid by the non resident parent. Even if you were to have 50/50 contact time the CSA would look at who has the CB as a measure of who teh resident parent is considered to be.
Hopefully you'd come to an agreement as to how much between yourselves as CSA seems dreadful from stories I've heard.