I'm no expert, but since no one else has chimed in I'll take a stab at it.
The 230 volt requirement is a nominal spec. Voltage varies from locality to locality and even from day to day. 240 should be fine.
Again, I'm no expert but perhaps the fifth wire is a neutral (3 hots, one ground, and one neutral). I've seen this sort of thing with 220 single phase welders. Instead of the normal 3 wire (2 hots, one ground) they often have a neutral wire as well. The neutral is only necessary if the machine taps one leg for a 110 application (such as a machinist light, a duplex outlet, dro, etc).