no.

I am not sure but I think I saw somewhere you need to set your pi hole as the DHCP server in order successfully resolve your local DNS entries, can’t remember where.

protonmail has been seen sharing it’s users data with 3rth parties. I assume that extends to all their services if necessary.

the “default” blocks malware

quad9[.]net/service/service-addresses-and-features/

who cares? share good privacy preserving tips. don’t agree? do you and see if it works out.