To assign names to individual IPs, you can either map them directly in the /etc/hosts file on the Pi, or use the Local DNS Records tab to map them in /etc/pihole/custom.list using the Pi-hole web admin interface.
It is possible, but you will need to use Pi-hole as your DHCP server and add a dnsmasq configuration file to do this.
You can assign all your regular clients to a new management group in Pi-hole, and assign all the current blocking to that group only. For the default group (where any clients not specifically assigned to the new group would reside), you can apply any blocking you want. All (by regex blocking the root domain), or no blocking at all (asssign no adlists or domains to the default group).