One thing that took me out of the film - the 80s pop music. 99 Luft Balloons? I love that song, but it's a relic of a happy, poppy 80s - which this certainly isn't.
Actually if you're going to use contemporary music, it's hard to do a better job than that since the song is a Cold War treatise about nuclear holocaust triggered by some misidentified balloons.
The sex scene was definitely supposed to be funny, but it was also supposed to be hot.
I'll eat my hat if any moment of that scene before the flamethrower is intended to be funny.