Kyle Clarke, 27, died when he was hit by a car in Hengrove, Bristol in January and was dragged along under the vehicle for 600m.
His mother Helen Stockford described him as the "light of her life".
In 2009, Kyle saved her from a convicted murderer and rapist who was on parole from prison.
Kyle interrupted Kenneth Shirley who had broken into the family home, raped his mother and planned to kill her.
Shirley, known by his middle name of Mark, had been released from prison on licence after serving 16 years of a life sentence for the ritualistic murder of a pensioner.
Mrs Stockford said her son had been badly affected by the incident and developed an eating disorder.
Following Shirley's conviction, which saw Mrs Stockford waive her anonymity to campaign for longer prison terms, Kyle had looked after her.
She said: "Over the dark seven years it's always been 'you alright today Mum? Is there anywhere we need to take you today Mum? Do you need me to do anything?
"What I miss most is, wherever he was, he would say 'night night mum', and I'm still waiting and that's crippled me.
"He was just so funny. There's so much you can say about him. He was the light of my life really. He was just so lovely, always joking, smiling, laughing."
Shakrun Islam, 30, from Chipping Sodbury is charged with Kyle's manslaughter.
He is to appear before Bristol Crown Court on Friday.

The 67-year-old was attacked outside his Gateshead home on 25 January and suffered a broken collar bone.
Beautician Katie Cutler, 21, began a campaign to raise £500 but the target was quickly smashed.
A 25-year-old man has been charged with intent to rob and will appear at Newcastle Crown Court on 24 February.
Mr Barnes and Ms Cutler had not met before she started the campaign but say they have since struck up a firm friendship.
He intends to use the money to buy a new home as he does not want to return to the area where he was attacked.
Mr Barnes has lived with disabilities from birth after his mother contracted German measles when she was pregnant. He is visually impaired and stands 4ft 6in (1.21m) tall.
He said: "I've always wanted to do other things that I've found difficult with having my eyesight problem but she seems to have opened doors and I might be able to do it now. It's sinking in."
According to the Go Fund Me site's terms and conditions, 7.4% is deducted from the total donation in administration and processing fees and 20p is deducted from each individual donation, equivalent to £29,389.20 from the £330,135 raised for Mr Barnes.
A gala ball at Newcastle's Assembly Rooms will stage another presentation ceremony on Friday. The event is by invitation only but 150 tickets were put on public sale, at a cost of £10 each.

The husband-and-wife duo overcame Indonesian pair Praveen Jordan and Debby Susanto 21-19 17-21 21-9.
It was the Adcocks' fifth straight win over the world number four ranked pair.
They will face China's Zheng Siwei and Chen Qingchen in Sunday's mixed doubles final.
Badminton is one of five sports to lose its UK Sport funding for the 2020 Olympics, but is appealing against the decision.
A woman whose son saved her from being killed by an intruder paid tribute to him as his funeral took place.
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Disabled mugging victim Alan Barnes has been presented with more than £300,000, raised through online donations.
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England's Gabby and Chris Adcock are one match from successfully defending their World Superseries Finals title in Dubai after a tense semi-final win.