He phoned two emergency departments, but was told that they were very busy and would not be able to treat him for more than 10 hours.
Busy with what? Chainsaw wounds are very dangerous and don't generally clean up that well even with going to the hospital
He said he could not afford an ambulance.
Doesn't Australia insurance cover any of the ambulance fees? If this was in the US everyone would be screaming about how these things happen here because we don't have universal healthcare.
As to the penalty I would think he could try and make the case for a kinda temporary insanity due to the pain and injury unless he had a history of driving drunk, for a reduced sentence