"Nut case" ????
Can we just use 'bad guy' instead of 'screwball'? It seems more generic and I presume has the same meaning.
A bit late to answer but from what I understand, dở hơi means crazy. So no, not the same meaning. But if Duo doesn't already, it should accept mad/crazy person etc
If a guy is "Dở hơi", his way of thinking is unpredictable, and not following common sense, it makes others feel weird and completely makes no sense. It sounds just like crazy, i guest.
A loose cannon perhaps?