Looking for a good guide on getting this setup via docker and AD LDAP, any pointers?

Who’s your DNS provider? I use cloudflare and powershell script and hits their API. Works well

Same but powershell. Works like a charm runs every 5 minutes

Yes

I would get a domain name and use ddns to update your rotating IP. Then I would setup wireguard VPN in split tunnel and have your parents network tunnel back to your piholes for dns resolution.

I use cloudflare API for ddns updates but there are plenty of choices for that. If you’re using cloudflare for DNS just keep in mind you can’t proxy the DNS entry for the ip for your VPN host as CF only forwards traffic over certain ports and they are not configurable (on free plan anyway not sure about paid).

Don’t get rid of it, install Kodi and/or Plex on it

+1 for dst nat on googles dns servers back to my piholes