Desperate situation with my parents, please try to help me?

well i am 21, me and my mum have been best friends for a year or so now. anyway, to put a loooong story short, they were having problems, my dad had depression and he was truly vile to my mum (no violence) he fought his way out of it in the end, but during the 7 months he was so nasty to her, my mum had had enough. she realised she doesnt love him anymore? after a few months, my mum has left to stay with her friend after telling dad its over, which broke his heart and he begged her for forgiveness. she said he is not to turn up at her work or where she is staying and he can only text her once a day, as she needs space. she tells me it is over, she feels nothing for him anymore. my dad is crushed he hasnt eaten for 5 days, he can barely speak or read properly anymore, and comes to mine and tells me how desperately awful he feels, and would do anything for a second chance. i have never seen him this way in my whole life. what can i do, please help?