You worry for no reason. It's not a simple trading platform that's going to snitch to the FBI because their system detected that you transferred $60 to the dark web just to buy a few pills 2-3 years back.

Besides, it would have to be the authorities to ask first and then the exchange gives the information.
It's not the exchange that contacts them saying "we have a user who sent 60 bucks on the dark web".

How could they know it was to buy pills? You can pay for legal stuff on the dark web too.

Either you want your 0.02BTC back and give what they ask for or if you don't want then...

Simply by means of blockchain analysis tools. Bitcoin is transparent but not anonymous

Any 'decent' exchange platform uses it for compliance nowadays. Most of them use the service of forensics companies such as Chainalysis or Eliptic.
Should I mention, when people use Binance for example, they do send some users' information to Chainalysis as it's their 'partner' and Binance's users (are supposed to) know it since it's mentioned (not explicitly) in their privacy ToS.

When you buy something from a DNM you get a BTC address to deposit, right? So it's easy to know an address that belongs to a DNM since I can create an account myself and generate one. Then, they identify clusters, from this point they have all addresses related to it.
Everyone can download the blockchain and convert it to a database to make some queries to analyze. Everyone can scrape Bitcoin addresses found on the www.

I can give you an example (not related to a DNM).
Yesterday I tried a website to buy bitcoins with a bank card, when it was needed to give the BTC address I gave one I found randomly on the web. I immediately got a message similar to: "This address has a bad reputation, we can't continue your order"

If you're worried to go through the KYC process because you think they can snitch you to the police then you worry for nothing. We're talking about 60 bucks, it's not like if we are talking about an address involved in human trafficking. If you're worried because you don't know what they're going to do with your personal data, or they can be the victim of a data breach, then it's something else but it's something people should wonder about before using a centralized exchange.

At the same time, your problem may not be related to your purchase on a DNM two years ago. Maybe you're playing at the casino, or something else against their ToS, I don't know.

My 0.02 BTC already became worth almost $ 1,000 and fox.exchange is not willing to send my money back (and they also refuse to proceed the exchange).

I've been in contact with fox.exchange for already three weeks. I have hand in my identity along with a proof of residence. I was offered to a video call in which I must proof the origin of my Bitcoins.

As mentioned in my very first post, it is impossible. I had withdrawn my Bitcoins more than 2.5 years ago from a marketplace in the deepweb, where I had purchased Adderall.

I just want my money back (or at least the swap to ETH). What can I do against this vicious fox.xchange ?