Does the lowpoly shading look good with the normal map applied? Hard edges are certainly useful to control the shading of the lowpoly, especially at steep angles - just remember to split the UVs along hard edges to avoid artifacts! Maybe check out Making sense of hard edges, uvs, normal maps and vertex counts?
it is an averaged normal, what are you expecting it to do? there are many edges pulling on that normal. if you want it to face foward, you could introduce a hard edge to the corner of the front gill. or you could manipulate that normal by hand. you could add more geo to compensate, or use normalmaps