https://www.goodreads.com/book/show/1098624.When_I_Say_No_I_Feel_Guilty
Its dated and probably misogynistic given the period, but when I did read it many many years ago, the broken record technique is probably the one thing I do remember. It also had some role play dialog for how others may try and break the loop. I found it helpful at the time.
I think I read/heard something similar in one of the Love and Logic parenting books/ebooks. "Maybe so, but " comes to mind. Acknowledge the statement that attempts to break the loop, don't add any new information, and repeat the assertion.
They can modify the DNS packets still. They aren't encrypted or signed so the authenticity of a response packet cannot be verified. Parental controls from ISP relay on being able to snoop and modify your DNS (and SNI from TLS ClientHello packets).