Iride01 

People think that fits should be cozy comfortable from the start. But that is not true IMO. It might be for those that are already fit or young and limber enough to be easily adaptable. My experience is that the heavier and more belly I have, then the more upright I have to be to feel comfortable. However for long rides that means a sore butt and more energy used due to drag. However after my winter weight and belly start going away I can feel more comfortable in a much more aero position with the bars much lower than the seat.

It's not natural for me though to want to be in that position. So I have to work at maintaining that position over the first couple dozen rides of the new riding season. But I know in my head the more aero I am the more energy I'll have left at the end of a four hour plus ride. Also that aero position will give me a more balanced body position over the BB that the opposing force to the power I'm putting into the pedals will lessen the load on my butt. With your saddle being further behind the bb it seems to me you'd not benefit as much from your power going into the pedals lifting some of your weight off the saddle.

So for you with short arms and your seat all the way back makes me wonder if it's the correct size or just not set up right. I have long arms and my seat on my 60cm Paramount frame from the 90's is pretty far forward one the rails with my handlebars fairly low with respect to the seat. I'm thinking about dropping the bars the last little bit of that adjustment I have left on that bike now that I've come to tolerate that position better. However when I first started riding again, my bars were about the same height as my seat.