R7000 dhcp challenge replacing Asus AC66u A1 and a Pi-Hole

Hi,

an unusual question perhaps but here I go.

I replaced my ac66u with an 2nd hand r7000.

I am running a pi hole 

i used to tweak my ac66u lan dhcp setting so it gave out my pi holes IP as dns to all clients.

because of this, all my clients show up separately in the pi hole logging.

now on my R7000 I can’t tweak the dhcp that finely. Only a range but no dns override.

I can change the wan dns but that gives me no control over the clients on the pi hole.

I tried to disable dhcp on the r7000 and setup the old asus ac66u as dhcp server in some role in my network, ap - bridge with dhcp on and with and without Nat and upnp and what not but results where unstable to say the least.

The two questions I have are,  

how do i give out custom dns to clients on my r7000 (stock):if possible?

or how would I configure the ac66u as dhcp behind the r7000 (dhcp disabled on the r7000) 

ap mode almost worked but my wired clients did not get an ip.

hope someone can help me to get this exotic situation up and running.

stock firmware on both but willing to swap.

thanks.