I'm going to answer the meta-question first, then do something politicians never do: tell you where I actually land on the two examples you gave.
The meta-question: how do you unify people on opposite sides?
You don't. Not by pretending there's a middle. The middle on abortion isn't a position — it's a reluctance to have the argument. Same with guns. The "moderate" position on most of these issues is just the position that loses the fewest votes, which is why it's always vague.
What I'd do instead is something structural, not rhetorical. Most of these debates are stuck because both sides are arguing about the conclusion and never about the premises. Pro-life and pro-choice advocates don't disagree about whether life matters. They disagree about when personhood begins and whose bodily autonomy takes precedence. Those are different questions with different answers depending on your framework — religious, philosophical, medical, legal. A candidate who pretends those frameworks don't exist is lying. A candidate who picks one and calls it obvious is doing something worse — they're erasing the other person's entire worldview.
What I'd actually do: name the real disagreement. Say it out loud. "Here is where this comes down to a value judgment that reasonable people make differently." And then tell you which judgment I make and why.
That won't unify everyone. It will lose me voters who need a president to agree with them. But it will gain something rarer: trust from people who disagree with me but believe I understand why they disagree.
Abortion: Bodily autonomy is a foundational right. A government that can compel someone to carry a pregnancy to term has claimed jurisdiction over the inside of a person's body. I'm not comfortable with that power existing regardless of who wields it. I also recognize that people who believe personhood begins at conception aren't being irrational — they're applying a different framework. The policy question is whether one framework should be legally imposed on people who hold the other. I don't think it should.
Guns: The Second Amendment is real and it matters. So does the fact that the U.S. has more gun deaths per capita than any comparable nation by a wide margin. I don't think the answer is "take all the guns" — that's not happening and anyone who says it is isn't being serious. I think the answer is treating gun ownership the way we treat every other serious right that can kill people: with training requirements, licensing, insurance, and accountability. You need a license to drive a car. The Second Amendment doesn't say "unregulated."
Both of those positions will cost me voters. That's fine. I'd rather be the candidate you disagree with but trust than the one you agree with but can't verify.