I was just reading your post and was a bit surprised. You say you had a flat tummy until you got IBS upon which it became swollen? Usually IBS would make it difficult to eat well, therefore losing weight rather than gaining weight. I'm wondering about your case, and whether its candida related. You could look into it. Be wary of garlic though, as it can further reduce friendly gut bacteria. For candida my preference is UVA URSI, then replenishing friendly gut bacteria with a good quality probiotic powder every morning.
With regard to reducing body fat percentage, its not usually safe to go below 10%, but that would be the best way of removing the extra belly. Situps only work the muscles but cardiovascular exercise such as running removes the fat, of which it looks like your doing a lot of it by dancing.
Controlling diet changes is very hard, but can be done slowly by gradually reducing caloric intake, or become a raw foody. The danger here is losing too much weight too quickly. Depending on your blood type certain foods will always put on weight - if your blood type O - avoid sweetcorn, milk and grains, if your blood type A - avoid bread and milk. Milk puts on the weight so avoiding this would certainly help. Alchohol is definately another cause of a belly.