If this was a real story, they’d find on CCTV that the door was opened with a key. Only other key would be with her sister - OPs mom - only other person with access to the key would be her son - OP. Who just a few days earlier tried to lie to his mom about going to college to grift some money. They search his room and find the goods. Rest depends on whether or not the aunt decides to press charges.
Excellent question. You can set the Pi-hole as a default DNS provider on your router which will the set it as a DNS provider for any device connected via DHCP (which in a home network should be basically everything). This means ads will be blocked across all devices and apps instead of just your browser where you installed adblock.