"It is in your best interest, and in the best interests of the community, that you... do something about your alcohol problems before it gets out of hand," Judge Alistair Garland told Fergus.
The court earlier heard how Fergus was drunk on October 10 when his mother refused to give him his car keys.
The process worker stormed off to his bedroom and returned with a samurai sword which he put it to his mother's throat.
Fergus, of Northwood in Christchurch, was originally charged with threatening to kill, and assault with a weapon.
But his mother was not injured and it was later reduced to one charge of threatening behaviour.
Judge Garland said the December 9 crash, where he had an excess breath alcohol reading of 518mcg per litre of breath - the limit is 400mcg - was a "serious accident".
But he praised Fergus, who has no prior convictions, for already paying for the damage.
The judge fined him $500 and disqualified him from driving for the minimum period of six months.
Defence counsel Andrew Bailey said the sword incident occurred during a "low point" of his client's mental health and alcohol consumption.
He had been bailed to live with his mother and she supported him, the lawyer said.
Fergus had been assessed to take part in the Bridge Programme for alcohol and drug addiction and was keen to address his "quite severe alcohol problems".
