I need some help. I'm trying to setup an ergoIRC(ircd) server behind my tailscale+mullvad+pihole VPN and a domain name registrar. I got the subdomain registered to the A record and created an API token, configured certbot and ddclient, and allowed the necessary ports in my router and firewall. I configured everything "correctly" but it won't connect. I think the issue lies in what public facing IP address I used. I used whatever is showing with my VPN enabled and I think that is what's fucking it up. Any suggestions with how to make this work?

Neither of your VPNs will allow for inbound connections. If you want to run a server, people will have to connect to your real IP address, which your router has; your VPN will serve no purpose whatsoever and you might as well disable it.