I obviously find what this guy did to be horrible. I can't say that I know what his punishment should be, but I do feel confident in saying that within a society where abortion is legal and men have no legal pathway to avoiding fatherhood once a pregnancy exists, 13 years seems excessive.
Whatever flaws our society had back when abortion was illegal, at least that society was consistent. It said that it was wrong to terminate a pregnancy, period.
Our current society is very inconsistent on these matters and in some troubling ways.
Woman gets pregnant, she has the option to abort it if she doesn't want to be a mother, and the father's desires don't even have to be a factor for her consideration if she doesn't want them to be. Once the pregnancy completes, she then has the option to STILL avoid being a mother if she wishes, by dropping the baby off at a fire department or putting it up for adoption. There are ways she can go through the adoption procedures without the father ever finding out. In fact, she can legally go through these scenarios without ever even informing the father that a pregnancy exists.
So women have an awful lot of options in this regard. Now, you might say "well yea they're the one who has to grow the child in their body for 9 months they should have more options!" - and okay, let's say I agree with you. Perhaps they should have more options. But men really have NO options:
If a man impregnates a woman he just has to buckle up and hope she is merciful. If she decides to screw him over, she can. She can dump him for no reason whatsoever, and use all the government's power to force him to pay an outrageous percentage of his personal income for the next 18 years even if the pregnancy was unintended, even if the condom broke, even if she lied and said she was on birth control when she wasn't, even if she pulled his condom out of the trash and impregnated herself with its contents, even if the couple had a standing agreement that she'd get an abortion if she got pregnant before they'd agreed to do so, etc etc etc.
Sometimes a judge will even decide it is in the child's interest to have the father pay for college after that 18 year mark. The courts really have the ability to do just about anything they wish to men, and most of this doesn't even bring with it much in the way of parental rights for the father, usually. He could end up paying for a child for years who he gets very little, if any access to. Sure, some courts will be better about giving him visitation than others, but this isn't very consistent and of course the woman can make up any lie about the father that she wants and the courts do not go to any trouble to try to verify that he really is the awful person she says, their default assumption is that she's telling the truth.
Now if people say "well she should get more protections and rights in this regard because women are the weaker, fairer sex and any society worth a crap cares more about them and protects them more." and if you were that society I spoke of earlier who didn't allow abortions, and had traditional values about gender roles, divorce, children, sexuality, etc... then you'd be consistent. Can't really fault 1900 America for saying something like that because it fit into the entire picture of their worldview perfectly well. On the other hand, 2014 America is being very inconsistent when it says, or acts in a way which says, that. Because it gives an awful lot of lib service to gender being irrelevant, the sexes being identical, etc. Again, it's the inconsistency that bothers a lot of us.
EDIT: Meant to say "lip service" but I think I like that typo, it works quite well.
How much punishment does a woman face if she uses spermicidal measures without the man knowing? In this scenario, she could tell him they were actively working to create a pregnancy, but she could be outright lying to his face and killing his living sperm, a part of his body, and she wouldn't face any punishment at all. I don't think she'd even be breaking any law at all.
A woman could tell a man they were working to get pregnant together and then the very last day that an abortion was still legal within the pregnancy, even if he'd bought a house for their family, and bought a crap load of carriages, cribs, toys, clothes, diapers... she could go get the abortion then come home and show him the receipt for it and say "PSYCH!!!! I planned this from the beginning!" and then leave him high and dry with all that stuff, and he'd have zero legal recourse.
So all I'm saying is, if we're going to leave abortion legal (and I am in fact pro-choice, with misgivings) then can we at least give men a couple of options?
Make some laws requiring notification of the father, and making finding him more of a requirement if she's putting it up for adoption. Make some laws against deceiving a man about pregnancy and sex.
And most of all, give men the "financial abortion" - the option to say, before a certain point in the pregnancy, "I do not want to be a father" and the legal right to sign away his parental rights and responsibilities, which the woman can react to by having the abortion, planning to put the baby up for adoption, or just deciding she can handle it on her own. Along with this there needs to be a legal requirement to inform the father in a timely fashion of the pregnancy so he can use this option. That's entirely fair and at least gives men some sort of control over their own reproductive rights.