Is the Filter Theory committing the ad hoc fallacy and is it unfalsifiable?

That is the part that makes no sense from the filter theory. Altering the message that got to grandma would be expected. But adding in that self-destructing aspect of the message, that simply makes no sense.

What does 'makes no sense' even mean in this context?  In this discussion?

1,000 years ago the idea of wireless communication would have 'made no sense' to the men/women of the day.

Its fine to doubt or question, but to try and apply your own woefully limited 'logic' to determine a firm stance on a theory is just shoddy thinking.  Better to leave it an open possibility, perhaps even one you strongly doubt but still leave the door cracked.

Ironically, you don't seem to struggle in the least with the huge explanatory gaps that remain in the materialist explanation for these phenomenon.

Its bias at the end of the day; something we're all guilty of for certain.