What is your style?
If your style doesn't work with pixels well, is it the fault of the pixels, or the fault of your style?
When you draw in photoshop, use the means photoshop provides. When you do pixel art, make art that utilizes pixels to their outmost.
No!
And wtf is going on with his arms? They're like stubs, where you've put the hands indicates a very uncomfortable position. Loosen it up, specifically the arm holding the staff.
I just don't feel the mixed rendering styles, you have some sprites and/or portraits painted, and some pixelled. Unless I'm wrong and you're going to pixel them all, why did you choose to make it that way? It makes it seem as if you are unsure of what you want to do, or don't care for consistency.
I also think the book open is fine. And he doesn't need to be looking at the book just because it's open, because perhaps he just read a line out of the book for memorization and is now focusing on the enemy. One thing to consider is maybe having him hold the staff out a bit further for a more epic, striking pose.
About the consistence part, I don't think it matters at all... you can use both Artwork and Sprites, there is no rule anywhere that says you have to make your own game X or Y way... what matters most is how it is executed, let's say do the sprites match well with the scenery and the art portraits? etc... you get my drift.