1) Make one of these: https://hackaday.com/2015/10/1...
2) Hand everything over. Warn the bad guys that if they try to use your USB stick, it'll fry their computer.
3) When they fry their computer, ask if they have learned their lesson about taking you on your word.
4) Be cooperative. You already won the battle of wits, be a gracious winner.
5) Your data was on your obscure self-hosted webserver elsewhere in the first place.
It is your destiny. - Darth Vader