Question: if I want to become a dark web researcher, how would I go about getting permission to do so without being suspected of being a malfeasant in the DW? Are there any authorities I can preemptively inform? I'm in the US.

What is your threat model exactly? The sites that will serve you up exotic malware are usually CSAM sites overtaken by feds.

You can browse without imagages, and no one has ever, once, in the history of the United States been prosecuted merely for an image in their cache, and there's plenty of sites that don't have that material to begin with.

Stop asking for permission, and challenge them to come find you if they have a problem.

(That's the problem they won't admit though: they can't.)