I do so much appreciate the work you have put into your website. I have consulted it regularly. I am in my late 60s. I obeyed the Gospel a few years ago and it has changed my life.
I was re-reading I Peter 3:15 and it became clear to me that I am not “ready” to explain to anyone who asks why I believe what I believe without burying them with an overly long and detailed response that will lose my audience, as well as the opportunity to tell them about what God has done for me and can do for them. I read God’s word daily and participate in several study sessions per week, but I’m not sure how to get started with synopsizing a response to ‘Why are you a Christian?” or “What makes you believe what you believe?" Is there a "best answer or is it something that is best explained through each Christian’s personal experience in coming to God? There are many tired old answers, like “Well, my family has always been Christian”, seem like something any Mormon, Catholic, or Muslim could say without making a distinction of why Christianity is the answer for me. How should I go about preparing the response that Peter is telling us to be ready with?
"Who is there to harm you if you prove zealous for what is good? But even if you should suffer for the sake of righteousness, you are blessed. And do not fear their intimidation, and do not be troubled, but sanctify Christ as Lord in your hearts, always being ready to make a defense to everyone who asks you to give an account for the hope that is in you, yet with gentleness and reverence; and keep a good conscience so that in the thing in which you are slandered, those who revile your good behavior in Christ will be put to shame. For it is better, if God should will it so, that you suffer for doing what is right rather than for doing what is wrong" (I Peter 3:13-17).
The context in which Peter speaks is that of persecution. There will be times on earth when people will mock the people of God for doing what is right, but like the prophets of old, God expects us to display unabashed courage to others.
"Then He said to me, 'Son of man, go to the house of Israel and speak with My words to them. For you are not being sent to a people of unintelligible speech or difficult language, but to the house of Israel, nor to many peoples of unintelligible speech or difficult language, whose words you cannot understand. But I have sent you to them who should listen to you; yet the house of Israel will not be willing to listen to you, since they are not willing to listen to Me. Surely the whole house of Israel is stubborn and obstinate. Behold, I have made your face as hard as their faces and your forehead as hard as their foreheads. Like emery harder than flint I have made your forehead. Do not be afraid of them or be dismayed before them, though they are a rebellious house.' Moreover, He said to me, 'Son of man, take into your heart all My words which I will speak to you and listen closely. Go to the exiles, to the sons of your people, and speak to them and tell them, whether they listen or not, 'Thus says the Lord GOD.' '" (Ezekiel 3:4-11).
"'Now, gird up your loins and arise, and speak to them all which I command you. Do not be dismayed before them, or I will dismay you before them. Now behold, I have made you today as a fortified city and as a pillar of iron and as walls of bronze against the whole land, to the kings of Judah, to its princes, to its priests and to the people of the land. They will fight against you, but they will not overcome you, for I am with you to deliver you,' declares the LORD" (Jeremiah 1:17-19).
Neither Ezekiel nor Jeremiah is told that he will convince the people he talks to; actually, they are both told the opposite. In the same way, I doubt the early Christians were always able to persuade their persecutors. It isn't the convincing that is important, but the attitude that I don't have to make an apology for living righteously and following after God. When I am asked why I am a Christian, I can politely but firmly explain the core of my belief. This gives God honor.
What you are doing is changing this into trying to convert people in one sitting. That isn't usually how it happens. Let's look at an example. You mention that abortion is wrong and someone gets in your face and yells, "What's the matter with you! Don't you care about women?" A simple answer, such as "I care about all people, and for that reason, I oppose the killing of children, especially when it is done for the convenience of the child's mother." The statement makes two unapologetic statements that get to the core of the issue. Delivered in a calm, gentle but firm manner will take most people by surprise.
One of the reasons I post my responses to hecklers on the website is in hopes of giving people ideas on what to say and the courage to stand up and say them. I know most hecklers won't listen to the answer, though a few have surprised me. The real audience is not the person opposing God but those watching you in order to see how you handle the situation.
Therefore, instead of looking for the ultimate reply, can you say in a sentence or two what convinced you to become a Christian, especially after all those years? Instead of aiming for an instant conversion, look to start a reasonable conversation. If the person seems interested or asks a question that can't be easily answered at the moment, set up a time to get together for a longer talk. Typically, most will avoid the meeting -- those are the ones who aren't really interested in learning the answers. But there will always be a few who are eager to learn a bit more. In this way, we set Christ apart in a place of honor in our hearts.