Daniel Spencer had a habit of taking revenge against those who crossed him as proved by his 21 previous offences which including harassment and witness intimidation, Wolverhampton Crown Court heard.
The relationship ended in October 2018 after two months and Spencer declared: "I really do hope somebody throws acid in her face" before hurling a liquid - which turned out to be harmless - over her head and spitting in her face on October 20.
Bricks and stones were thrown through windows at the family's Great Wyrley home causing up to £4,500 damage but luckily a lit firework - with Spencer's DNA on it - missed the hole made in the lounge window and was found on the ground outside on November 29.
Spencer, aged 23, threatened to blow the family's house "to smithereens" if his former girlfriend did not drop the case against him.
He was arrested on January 29 last year but continued to put her under pressure with threats issued for the prison while held on remand.
Mr Antonie Muller, prosecuting, said: "The stalking was long and persistent causing very serious distress to the young woman and her family."
An emergency phone line to the police was installed at their home and a dash cam fitted to the front door filmed two hooded men throwing a blazing rag soaked in petrol under the family's Toyota, parked a foot from the front bay window January 23.
Petrol was bought by Spencer just 15 minutes before the arson attack, in which 35-year-old Andrew Langham took part.
The girl's father rushed out to find the bonnet and a tyre alight and was helped by a neighbour to extinguish the flames that threatened the house.
The prosecutor declared: "It was an act of revenge that put many people at risk."
The victim revealed later: "My family and I lived in constant fear of what he and his friends would do next."
Mr Timothy Sapwell, defending Spencer, originally of Horseley Fields in Wolverhampton, said: "He is horrified by the way he behaved and is sorry for the stress he put people through."
Mr Jollyon Robertson, representing Langham, of Russell Close, Ashmore Park, declared: "He was only involved for a very short period."
Spencer and Langham, who was jailed for three years, admitted conspiracy to commit arson.
Spencer also pleaded guilty to stalking, attempting to pervert the course of justice and harassment.
Judge Michael Challinor, who jailed and banned Spencer from any contact with the girl and her family for ten years, said: "Your catalogue of offences was designed to worry and ultimately terrorise the victim and her family."