PC David Rathband, 44, who was blinded by gunman Raoul Moat, had won national praise for the way he tackled his new disability, creating the Blue Lamp Foundation to help emergency workers injured at work.
But after attending the trial of two of Moat's accomplices in the spring of 2011, he lost motivation and had failed to adjust to losing his sight, his widow Kath told the inquest at Newcastle's Moot Hall.
In February 2012, he was found hanging at the three-storey townhouse in Blyth, Northumberland, he moved into following a domestic incident with his wife.
Mrs Rathband, mother of 21-year-old Ash and Mia, 15, said her husband had several affairs with women, but his last with Lisa French, a survivor of the London bombing, ended their marriage.
"By this point it was my opinion our marriage was over due to David's level of deceit," the widow told the inquest.
She said she had always forgiven him for his previous affairs.
"This was the one and only occasion I felt me and the kids had had enough," she said.
Both women gave evidence at the hearing, which was also attended by his two sisters and his father Keith.
Mrs Rathband found out that the friendship, which started on Twitter, had become more serious just days before her husband flew to Australia to visit his twin, Darren.
Mrs Rathband told the inquest he could not understand why she would not take him back, and would call her up to 100 times a day.
It became so bad she enlisted the support of the Domestic Violence Unit, she told the inquest.
Mr Rathband, who was born in Stoke-on-Trent, would send abusive messages and would sometimes threaten to self-harm. But his wife said the pattern was for him to send unpleasant messages to her but to be calm and rational when she spoke directly to him.
From Australia, Mr Rathband called her pretending to be a police officer announcing his death, and then said "You will see a fluorescent jacket at the door" - a reference to how the news would be broken to her by the emergency services.
Before blasting the unarmed traffic officer, Moat shot and injured his ex-girlfriend Samantha Stobbart, and killed her boyfriend, 29-year-old Chris Brown.
Moat shot himself in Rothbury, Northumberland, during a standoff with police at the end of a week-long manhunt.
The inquest continues.