question 1 Why do I only see my router's IP address instead of individual devices in the Top Clients section and Query Log?
also make sure the DCHP server built into your roputer is handing out the pi-hole address and not the router address that usually helps
question 2 . Unless you need all devices to have a publicly accessible IP address just turn off IPv6 Altogether. there is really no advantage as most ipv6 doesn't do static near as well as IPv4