All the words technically do exist, even though you won't find them in bilingual dictionaries as well as in many monolingual dictionaries.
If you take a look at a more historic dictionary, however, you realise that all the words at least used to exist.
KURZWEILEN , kurzweil treiben u. ä., ein seit dem 18. jahrh. abgekommenes schönes wort (langweilen gibts noch)
You can find Kurzweiler in the dictionary, too.
Langweil is spelled with an e at the end, but it's indeed the opposite to Kurzweil. According to Grimm'sche Wörterbuch, Langweil without an e exists since the 16th century, though.
allerdings ist lángweil doch auch entwickelt, in oberd. mundarten oder denen überhaupt, die das -e gern abstoszen
On the other hand, you might also find some texts with Kurzweile — with an e at the end, that is.
And if you read on in Grimm'sche Wörterbuch, you also learn that Langweil(e) used to be two words, while Kurzweil(e) has always been one word. Well, except that there are a few occurrences where it was split up into two words. But that's another story.
And on another side note, langwierig and kurzwierig (or Langwierigkeit and Kurzwierigkeit, respectively) is also a word pair where only one is common in contemporary German.
So, how come some words are not used any more but others are? Well, that's the secret of languages evolving over time. Or just because there's no need for certain words.