Gosh, he's defintely not right.
I am so sorry.
I agree with-your mom, actually. But you still have to have your own life.
Please get your dad to a doctor. Considering he monitors the GPS and cell ph calls, there's no way you can outsmart him and he will have to be told the truth. And you may all have to give him an ultimatum, or an intervention which, unfortunately, would not go down well, considering his paranoia.
Is there any way you can get someone to come into the house, a 3rd party soc wkr or something, to help facilitate a sort of intervention?
Does he leave the house very often?
I am so sorry for your difficult child. His position is completely understandable.
{{{Many hugs.}}}