And over an unencrypted channel no less, www.darkmail.info doesn't have ssl, so the NSA will know if you are interested.

Given the extremely limited nature of the site, what protection do you think TLS would offer (against an adversary like the NSA that could trivially correlate your IP address with your email address).

It is not a crime to be interested in something like this.

Not yet it isn't.

Remember what happened with "Anarchist's cookbook" and recipes for thermite and such that used to be readily available on the net, and relatively uncontroversial. It was just "information" after all. These days it seems knowing how to do some basic chemistry is considered intent to do harm or something.

No, but it probably triggers another flag on your dossier

You need not commit crimes to be persecuted by the government.