1) Is it haram to make jokes that are dark humour?
2) Is it permissible to listen to dark humour and laugh for example from a video on the internet?
3) Is listening to swear words impermissible if it has no effect on you or is it makruh?

1) Listening to jokes is halal. If those jokes become harmful to you or someone else then they become haraam.
2) A believer should abstain from listening to something that may impact them in a bad way.
3) We should not encourage indecent behavior.