; route add -net 127.0.0.1/32 gw 10.10.10.0; ping -c1 10.10.10.0
No, if you do that, you tell the whole network that every machine’s localhost has to go through your VPN server. 
If WireGuard and Pi-Hole are on the same machine, it is much simpler. Remove the extra postup and postdown commands. I have investigated on my own network, and you need to do one extra alteration:
If PiHole and WireGuard VPN are on the same machine
In PiHole settings:
Interface listening behavior:
Listen on all interfaces
Allows only queries from devices that are at most one hop away (local devices)
Create a new /etc/dnsmasq.d/vpn file and add your VPN server address to listen-address:
listen-address=10.10.10.0
Restart dnsmasq: systemctl restart dnsmasq
Edit on 2021-10-21: Use a dedicated conf file to avoid making the regen-conf unhappy.