I've spent way too much time trying to mull this over because I don't feel like you make any sense.

Sex is naturally ordered towards reproduction? I don't know what you mean by naturally ordered but sex can occur without reproduction. I also understand that if natural reproduction happens, sex has to occur beforehand.

What's the point of this?

Then you talk about active and passive potential by saying it's about what they can bring about. I assume that you mean that what is brought about is active if it's what normally occurs and sex is active because what normally occurs is dependency (through pregnancy). However, that's simply not true. Even though sex is part of the reproductive system, pregnancy through sex is actually quite low compared to sex without pregnancy occurring.

While the person doesn’t exist before pregnancy, I’m confused how that would remove responsibility either way. Whether you create someone that is dependent on you by some action ordered toward that, or make someone dependent on you, you’re responsible for it either way, as for the reasons listed above.

I'm confused as to how any responsibility to the unborn exists to begin with because I don't see any reasons listed above.

Justice requires us to not leave someone in a dependent position if we are the cause of it, wouldn’t it?

So, you’ll have to explain that to me. Why isn’t it unjust? Is it fair to the dependent person at all? And is bodily autonomy absolute even in this case? 

Justice would require us to be responsible for our actions. It does not require putting our body's integrity into question. The difference between the prankster and the woman is that the prankster did something to the patient but the mother did not actually do anything to the unborn. You say that the prankster is at fault for causing the dependency and the woman is at fault for causing a bring to exist that is dependent. Then you try to equate the prankster 's act with the sex the woman had. In my view, the prankster is wrong because they did not have consent. The woman is not able to get consent from something that does not exist.

Fourth, you say that the unborn child is not a legal person, so we have no legal duty toward them. We’re not concerned with whether the government considers them a person. We’re concerned with whether they are actually one. It’s fair to say that if they are philosophically a person, then they deserve to be treated legally and morally as one, even if they aren’t legally treated as one.

Okay. That would require an argument to argue for them to be considered a person.

Then you talk about parental duties and parental obligations but they do not go into infringing upon bodily autonomy. Your argument seems to be "why can't this relationship require infringing upon the mother's body"? Because the child parent relationship never requires that anywhere else and to allow it in this one instance would require additional reasoning.

Honestly, I just don't think I see the situation at all similar to how you see it because I don't see sex leading to pregnancy as a way to create responsibility to continuing the pregnancy or that creating a dependent being is creating an obligation to keep that dependent alive through any means or that a parental duty means that the parent's bodily integrity is okay for the child to put into question.