Genetics play a role in where fat gets lost from first / last. All you can do is keep losing fat until your body removes the fat from that area.

Sit ups / stomach work will not target your stomach fat directly - it doesnt work like that. It will tone the muscles, but if you still have fat to lose then that will be sat on top.

Hope this helps, keep up the hard work and the results will come your way. You seem to be on the right track, and im sure its not half as bad as you think!