I'm having a lot of fun with this. Here's my thoughts, in brief:
-I like the story. It's not fantastic, but it's good. You really have a knack for fleshing out character relations.
-The maps are about the same quality as the published games, which is nice. I don't know if you made all the maps or what, but they're really doing it for me. The foggy map (I think CH 16 or something) was especially good.
-You are right about the difficulty being backwards. I think the Prologue and Chapter 1 are the hardest chapters, at least on normal mode. Overall it's a pretty challenging game until you get your first promotion, which happens pretty quickly because you starting getting promotion items like candy after the chapters go into the double digits. With stat items and literally everyone having good growths, some units can actually reach multiple capped stats (and I'm sure that with favoritism in play, one could potentially get a unit with nearly every primary stat over 30). I also felt that getting an arrow shield pretty early didn't help things, because once I got that Keiran could basically just take on entire halves of each chapter by himself, though I guess the prevalence of lightning magic is a fair trade.
-Not necessarily related to difficulty, and personal experience is in play here, but the pre-promoted units (Rayden and the Wyvern Lord, Josephine I think) seem to be a lot better than one would usually expect a Jeigan unit to be, was this an intentional subversion of jeiganism or did I just get lucky?
-I like what you did with the dancer, both getting her late and her being more than the one-trick-pony most dancers are.