I'm sorry, but allowing him to come home will result in the abuse starting again. There will be drug use in your home, around your children. Your AH is full of bulls**t.
Do you notice how he is putting the responsibility for all this "pain and suffering" on YOU? As though you are the one that chose drugs over a family, or put selfishness in front of responsibility?? What a load of crap.
HE is responsible for his own situation. HIS choices landed him outside of his comfort zone.
The more you talk to him or read his emails or listen to his voicemails, the more he will worm his way back into your emotions. STOP NOW.
It isn't easy. But what do you really want for your life? You only have two choices really: go back to the same way it was before or go forward alone for now.
Because I am telling you, YOUR AH HAS NOT AND WILL NOT CHANGE AS OF NOW.