Hey Quokimbo, Your texture needs a lot of work. First off youre wasting more than half the texture map leaving it blank like that ideally all space on your color map should be filled with detail you created. Seeing that your prop doesn't justify the use of a 512x512 go ahead and crop the texture down to 512x256 textures…
I am reading about this normal mapping stuff as I read your post. Still kind of lost though. found this? http://www.bencloward.com/tutorials_normal_maps4.shtml