Complex sentence: He's an idiot when it comes to making new, miserable ideas and relies on Heloise's inventions, which he inevitably takes credit for; but if something goes wrong, of course, he is quick to blame Heloise.
Split into simpler sentences: He's an idiot when it comes to making up new, miserable ideas and relies totally on Heloise's inventions. Which he has been known to inevitably takes credit for; but if something goes wrong, he blame Heloise.