The man was often confrontational giving evidence at the Brisbane inquest into the boy's death, pushing back at suggestions he had changed his story and tried to manipulate witnesses.
His two young sons suffered devastating burns in an "off-grid" house at a rural property in southeast Queensland in 2017.
His pre-school aged boy later died in hospital after being airlifted by helicopter.
The family cannot be named for legal reasons.
The father completed three hours of evidence on Wednesday which at times featured expletive-laden outbursts as he lambasted counsel assisting Kate Juhasz.
The father frequently interrupted Ms Juhasz, accusing her of asking irrelevant questions to drive a "narrative that's not true".
It prompted coroner Megan Fairweather to ask the father to show respect for the court process that was trying to find out why his son died.
"If you could just answer questions to the best of your ability with appropriate language for a court setting," she said, adding she would intervene if Ms Juhasz was unfair to the father who was not legally represented.
He testified that he woke and entered the boys' bedroom to find a small fire that rapidly exploded into a fireball.
"By accident were you involved in starting the fire in some way?" Ms Juhasz asked the father.
"No," he said.
He was then reminded of his surviving son's comment about his father: "He made the fire ... with his lighter. He used the lighter on my clothes."
Asked if he used a lighter to burn his son's clothes or belongings on the day or night of the fire, he replied: "I don't believe so".
The inquest had earlier heard the father was living with his two sons in an off grid dwelling 150 metres across a paddock from his parent's home.
The father denied a suggestion he burnt some clothes to teach his sons a lesson for having a messy room.
"You come into the boys' rooms. As you told police there's toys and clothes strewn all over the floor again," Ms Juhasz said.
"To teach them a lesson you burned some of the clothes and put them on the ground in that room and you thought you put it out?"
The father replied: "I would not light a fire inside the house".
His surviving son might have been confused by him earlier burning a pile of rubbish that could have contained the boy's worn-out or stained clothes, he said.
The father was also asked if he might have been drinking alcohol and been upset over the boys' mother fighting him for custody.
He said he could not remember events, dates or details.
"I have spent thousands of dollars having these memories erased by psychologists and hypnosis," the father said.
"I don't know what benefit I can be to you."
Ms Fairweather offered her condolences to the father and his family members over the loss of the young boy at the closing of the inquest on Wednesday.
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