I would say, HELLA FRICKEN NO WAY!!! No way would that happen, after just one visit and some clothing??? Heck No!!!
He would have to prove himself over and over and over and over again, to start with child support for a year and half the doctor bills or anything you had to pay for while he was on his sabaticle (JERK).
I hate with a passion that there are men out there who drop the women they supposedly loved and then come back after the baby is born or years later to take credit for something they had nothing to do with but DONATE SPERM. What a JERK!!!
Before you make your decision to change, which I hope you will not, remember the loneliness you felt, remember the embarrasement, remember the times you had to carry your own groceries, and much more remember being dumped as a nothing while you carried and cared for this child who was dumpled as well.
I am sorry but I 100% disagree with changing the babies name and after all this time, I am surprised you would even want him to be in your life again, he does not deserve you nor the baby.
I would say, out the door, dont let the door hit ya where the good lord split ya!