It says in the notes that the -t is for ett words... why does "det" (it) get the -t ending as well?
Only if you're referring to a specific en-word, like for example "Titeln är påhittad. Den är inte officiell." ("The title is made up. It is not official.") Only "det" can be used as a dummy subject.
Minor quibble, but i accidentally spelt id instead of is and it still failed me for such a minor typo.
In Swedish could you use this to describe a romantic relationship like we do in English?
Native speaker here: It's not the first meaning that comes to mind, but I would say you can.
try saying that to all the fnaf fans who prefer tjoc (you have to be a fan of five nights at Freddy's and its fanbase to understand this joke)