Seems like your router's DHCP server is still active, distributing itself 192.168.1.1 as DNS server.
If your client is running Windows, you could verify this by running:
ipconfig /all | find /i "server"
The option is unchecked on in my router settings
no mac actually
That sounds a bit contradictive - is it unchecked or on?
As nslookup output clearly shows that your client is using your router for DNS, that means either your router is still running DHCP or your client hasn't renewed it's DHCP lease yet.
Can you ping your Pi-hole's IP from your Mac client?
You can ping Pi-hole, but not use it for DNS.
Do you run a firewall on your Pi-hole machine that would block DNS or DHCP ports?
Thank you, but that just shows what ports are bound, not which ones are blocked - and part of that is already in your debug log anyway.
By the way, you can check the log, it's located at /var/log/pihole_debug.log and it is meant to be consulted by users and us for troubleshooting.
I just noticed I misspelled the second nslookup command.
Could you rerun and post the output for:
nslookup flurry.com 192.168.1.11
And I've got help from a colleague with mac knowledge now to back me up.
You could run the following on your Mac to show your DHCP server:
ipconfig getpacket en0 | grep "server_identifier"
You may have to change en0 to en1 if you use WiFi or Ethernet.
ipconfig:
server_identifier (ip): 192.168.1.1
nslookup:
:: connection timed out; no servers could be reached
The first one shows your Mac is still seeing your router as DHCP, while the second confirms you cannot resolve DNS through Pi-hole.
Both could be explained by a firewall blocking DNS and DHCP ports.
As you run a few additional software packages, those might have activated iptables rules on your RPi.
A quick test would be to run
sudo iptables -L
However, that is not the only possible firewall package, and configuration would depend on which one you run.
I am afraid I have to catch some sleep now, it is way past midnight for me (I am in Europe) - I'll ask my fellow team members to keep looking after you. 
@jfb, can you have a look here, please?
Thanks for your help!
Let's focus on the Mac and see what is using for DNS. If needed, we will manually map Pi-hole as DNS on this device and test that way. From the Mac terminal (and not via ssh session to the Pi-hole), what is the output of the following:
cat /etc/resolv.conf | grep nameserver
cat call returns:
nameserver 192.168.1.1
OK. This client is using the router as the nameserver, and it appears the router is not properly routing the DNS traffic to the Pi-hole. Let's bypass the router and go directly to Pi-hole for DNS.
System preferences > Network > Advanced > DNS.
Add the DNS server with the IP of your Pi-hole (and no others) - 192.168.1.11.
Click OK, then click Apply. Now the Mac should be using Pi-hole for DNS.
From the Mac terminal, run nslookup pi.hole and post the output.
;; connection timed out; no servers could be reached
What nameserver is the Mac using now? Again from the Mac terminal:
cat /etc/resolv.conf | grep nameserver
If this shows that Pi-hole is the only DNS server, then the problem lies in your network configuration. Something is blocking DNS traffic from getting to the Pi-hole.
I get:
nameserver 192.168.1.1