*has been traveling and only just got to this today*
Your book is good. Write it.
I basically agree with what the others have said— that there’s a place for darkness and stories that are hard to tell because of the sorrow they carry. And it sounds like you’re being smart about this; you know your target audience and you’re writing for them. And, honestly, I think we need more books that deal with the type of issues you say come up. Not all Christian fantasy is rainbows and unicorns and fluffy romance. (For evidence: Tales of Goldstone Wood. The Wingfeather Saga. The Ilyon Chronicles. Plenilune. The aforementioned Songkeeper Chronicles. Most of Bryan Davis’s books, although he can get a little preachy at times.) However, I will agree that a good bit of it is. And even the existing books cover a limited number of topics.
So, yeah. Write your book. And if you want to send me scenes to get my opinion, or if you need a beta for the full book, just let me know. (Just, maybe not in the next week, because I’ll be on a semi-hiatus and might not respond very fast.)
Welcome to the masquerade.