Don't limit yourself. Lots of fiction has been written from a "Christian" perspective without it being obvious. (In fact, until about the last 100 years, most fiction in the West was written from a Christian perspective. That is, it took for granted that mankind is flawed, but basically good, and that Good as well as Evil exist.) If you write solely to a "Christian" audience, then you are ignoring all those souls out there who need to know that life, though often hard, is good, and that internal change is possible. That's why most of us love the old novels the best.
In brief, avoid nihilism. It's the pose that has, for the last 100 years, run art straight into the ground. If life is meaningless, why even write about it? If beauty does not exist, why paint it? It's a mental attitude of despair and cynicism that holds life and mankind as worthless. Fiction used to be a journey in which the reader accompanied the writer through an imaginary world of moral choice: Good and Evil exist---though they are not always clearly distinguishable---and their battle is fundamental to the story. That dynamic tension, in fact, is the main reason why any story is interesting. (Read Aristotle's Poetics.)
If you write with an intense love and interest in the fascinating world God has allowed us to enter, and if your characters are interesting and complex, and if they struggle with moral choices, or to overcome personal frailties---yet overcome---then you are writing as a Christian. Christian art affirms the basic goodness of this life, even in its complexity, and it does not succumb to despair. Dostoyevsky was above reproach, wasn't he?
I also love Lisa's suggestion about leaving some details the the reader's imagination. In Greek tragedy, the murder used to be committed off-stage because it was far more effective to leave it to the imaginations of the audience. A good novelist allows his reader to participate.
As far as writing about things Orthodox for a career--writing novels isn't going to pay the bills--develop interviewing skills and a solid nonfiction style. There's always room for a good article writer. Now that pays.