The obvious thing I noticed is that the lowest point of the seat is NOT in the center of the saddle, as it sits on your horse. That would throw you back and give you a chair seat (chair seat is where your legs are in front of an imaginary line draw from your shoulder, through your hip, down to where your heel SHOULD be). Ideally, that line should be straight and vertical. Even if the saddle fits your horse--and it doesn't sound like it does--it doesn't fit YOU, and the saddle throwing you back is not good for your horse, either. I would not keep that saddle if I were you.
And as flakemusic said, you need someone knowledgeable in saddle fit to look at and palpate the saddle's fit on the horse. We can't do that here.