That doesn't answer my question. 
I can tell from your debug log that your router is correctly configured to distribute your Pi-hole's IPv4 address as local DNS resolver viua DHCP.
But did you configure your router to also use Pi-hole as its upstream DNS server (commonly, a WAN/Internet sort of option in your router)?
EdIt: If so, you could possibly try Dnsmasq[1035]: Maximum number of concurrent DNS queries reached (max: 150) - #2 by Bucking_Horn