回复：妈妈的信-我好痛,请耐心看行吗?

I think you should write to your dad, show him your mom's email and tell him your feeling about him, about your mom, about this family and the life.
Maybe it's better your mom is not at his side when he get your letter so he could have time for himself to think over his behavior.
Your dad is kind of person that could not think in other's shoe. I am not saying he is bad person. He might just need somebody else to remind him,
let him realize his problem. When people get older, they will be softer. You said he was showing that sign already, right?