All too often, people (including family members and friends we are prone to go to first) get defensive and don't seem to care as much about the person who is struggling as much as they seem to care about protecting their own beliefs. We need more empathy all around. Less worry and more love. I recommend Richard Bushman's pastoral approach.
I don't have a lot of experience in this realm. But I've had enough to feel prompted to share some thoughts. Sometimes when people present their concerns to those who haven't yet assimilated those facts into their own faith paradigm, problems arise in communication. That's when concern for the "one" rather than concern for ourselves should kick into gear. That concern is exactly what Elder Wirthlin was talking about in his now classic conference talk: "Concern for the One".
I tried to do this, in my own imperfect way for sure, in response to an email I received several months ago:
I appreciate you writing and feeling confident enough to ask your questions honestly and openly, and share your concerns with an "outsider". I sense your sincerity and I hope something I say can be helpful. First off, let me just say that you're not alone; you're not the first to have struggled with these questions. I hope it can give you hope to say that passing through doubts with your beliefs still in tact can actually strengthen your testimony. And in some respects, I think all of us live continue to live with doubt to some degree.
One thing I do know--"know" undeniably--is that I have had some very powerful, spiritual experiences with the Book of Mormon, and I always come back to that. That's the foundation of my testimony. There are many things I'm not 100% sure of, but I always come back to the Book of Mormon and the implications which it carries with it (ie: God does live and reaches out to bless his children, Jesus is the Christ and really did live, die, and take up his life again, etc). Naturally, it is the single greatest evidence of the prophetic mission of Joseph Smith. Joseph had many flaws for sure, but as Elder Holland's fourth great-grandfather said when he heard of the Book of Mormon in England, he walked away from the service saying "no good man would have written that, and no bad man could have written it." It still remains the single greatest evidence for the prophetic calling of Joseph Smith. So even though Joseph isn't perfect, and the Church isn't perfect (because it's made up of very imperfect individuals)--the gospel of Jesus Christ is perfect and I cling to that. And I find that gospel taught powerfully in the Book of Mormon, and I recognize God's fingerprints all throughout that book. That's why I believe.
It's easy to doubt. It's a little harder to have faith, but that is the path that I have walked, even as I've had to adjust my framework of the Restoration as I've learned more. I once wrote on my blog: "I stubbornly desire to remain open minded yet filled with faith at the same time. I appreciate what President Hugh B. Brown said about doubt: 'Some say that the open-minded leave room for doubt. But I believe we should doubt some of the things we hear. Doubt has a place if it can stir in one an interest to go out and find the truth for one's self' ("An Abundant Life")."
I don't think it would be as helpful to focus your concern on whether "the Church is true", because there are some things that does mean and some things it does not mean, and it's easy to miss the boat and confuse the issues. That's why I'd say start by focusing on the Book of Mormon; focus on goodness--focus on true joy. Start with what you DO know and go from there. I don't think it's particularly helpful to have too many concerns/doubts floating around in your head all at once. But keep in mind that there will always be other, more positive perspectives that you can accommodate into your testimony than that which is offered only by the critics of the Church. They have an agenda, and it's not always as fair as they want you to believe.
Last thing, if you truly want to know truth, you also need to make sure you're sincerely trying to keep the commandments, otherwise you won't always be able to distinguish light from darkness, and sometimes guilt can sway your perspective. Like Jesus said: "If any man will do his will, he shall know of the doctrine, whether it be of God, or whether I speak of myself." (John 7:17).
My heart goes out to you. You're in for quite an adventure. It might be a struggle, but you have every right to know for yourself if all this good news is really true, or if, as you said, it's like Santa Claus. I'll share with you my conviction--this isn't just a fairy tale or pie in the sky. It's really the greatest, most important knowledge to know that God lives and that Jesus is our Savior. This life has purpose. We didn't come hear just to live and die and have that be the end. I have an atheist co-worker, and while she is a fantastic person, she sure is missing out on at least living with more hope (see Ether 12:4). Because even if it weren't true, it can sure bring a lot of happiness and goodness to how we live our life.
You talked about fear. Faith really is letting go of your fear and turning yourself completely over to Christ. Only then do you truly find rest for your soul. You also talked about "knowing" versus just being "pretty sure". Here's how I've come to know, versus merely have faith, on some of these issues. Read Alma 32, at least from verse 26 on, where Alma compares "the word" to a seed. The power comes from actually reading in the Book of Mormon, but here is my paraphrase:
He says that when you plant a seed, do you "know" if it is a good seed? No, but you have faith. But as the seed begins to grow, and if you nourish it and don't cast it off because of unbelief, then it continues to grow, and then you stop needing to have faith that it was a good seed, but now you actually know it was a good seed. And if you continue to nourish it, it eventually grows into a tree which bears fruit. When you partake of the fruit, when it has enlarged your soul, enlightened your understanding, and it is delicious to you--you no longer have faith in that seed. You KNOW. And that's how I know what I know.
Alma goes on to say in Chapter 33, verse 23, his concluding remarks: "And now…I desire that ye shall plant this word in your hearts, and as it beginneth to swell even so nourish it by your faith. And behold, it will become a tree, springing up in you unto everlasting life. And then may God grant unto you that your burdens may be light, through the joy of his Son. And even all this can ye do if ye will. Amen." So this is the "experiment" that he recommends. I guess I recommend it too. :)
PS: Although I have never felt it personally necessary, I know some have found the following website helpful. If the advice I gave isn't quite what you're looking for, it may or may not have something you are looking for: www.staylds.com