Connor Webster continued to harass and threaten the victim after he was arrested over the attack and bailed with conditions not to contact her.
Leeds Crown Court heard the 23-year-old almost caused a crash when he pulled the handbrake during the incident in September last year.
The court heard Webster became angry when his partner told him she was going for a night out with her friends but he was not invited to go with them.
Before pulling the handbrake, Webster said: "I have nothing to live for. I may as well kill us both."
The vehicle skidded but the victim managed to keep it under control.
Webster refused to get out of the car and attacked the woman as they were park in the car park of Homebase.
Fiona Clancy, prosecuting, said Webster bent the woman's fingers back, punched the rear view mirror and then punched here in the eye.
He eventually left the car after an hour.
Ms Clancy said Webster continued to harass the woman after being released on police bail.
Over the course of ten weeks he rang her from withheld numbers.
He made threats to put the victim's mother "six-foot under."
On November 9 the victim left her home to go to work and saw that plants outside the property had been disturbed.
She then noticed the words "I was here" written in condensation on the bonnet of the car.
On another occasion her car tyres were slashed.
Webster put information about the victim on Snapchat and threatened to post images.
Martin Morrow, mitigating, said Webster was sorry for what he had done and was struggling with mental health issues at the time of the incident.
Mr Morrow said Webster has been diagnosed with depression and anxiety.
He added that Webster is in a new relationship and is hoping to begin studies with the Open University.
Webster was given an eight-month prison sentence, suspended for two years.
He was also ordered to complete 30 rehabilitation activity requirement days.
Judge Neil Clark said: "You pulled the handbrake at 50mph, causing the vehicle to skid.
"That was stupid and potentially lethal."