He was good on paper: Eloquent, mature, healthy and smart to boot. That’s why Angela Collins and Margaret Elizabeth Hanson say they chose Donor 9623 to be the biological father of their child.Then last June, almost seven years after Collins gave birth to a son conceived with his sperm, they got a batch of emails from the sperm bank that unexpectedly — and perhaps mistakenly — included the donor’s name. That set them on a sleuthing mission that quickly revealed he is schizophrenic, dropped out of college and had been arrested for burglary, they said in a lawsuit filed March 31 in Atlanta.