Oh my, I'm a stylist. The breakage is most likely from the flat iron and the rollers, that's why it looks like a broom, b/c it's dried out. As for the elastic, it can cause breakage also, but use it careful and it wont. As in, don't wrap it very tightly and do not use it when hair is still wet.
Do you have any wave to your hair? If so, I would cut it just passed your shoulders, maybe with an angled bang, so you don't have to fight for straightening all the time. Have it a tad longer in the front and shorter in the back, with some layers to help remove the weight and the damage, and so you can gt more volume in the top. If done right, it can help you get a bit of a wave to it, or even look right if you decide to flat iron it. You can even use your flat iron to create waves. Why am I suggesting waves? Because they help mask damage, and give you a new look and aren't typically as damaging.
Be sure you use a thermal styling protection spray on your hair, like Paul Mitchell's Heat Shine prior to ironing. And if those jumbo rollers are heated, don't do those and ironing at the same time. If they are velcro, be very careful when pulling out, they can break hair off too.
My all time favorite product for coarse, damaged hair is Sebastion's potion 9. You put it in your hair when it's still damp and it really helps tame and moisturize. Also, be careful with blow drying,,, don't blow dry until your hair is about 75% air dry to help reduce further heat damage.
My hair is a lot like yours and I do the pony tail thing a lot too. Play with how you do it, try a deep side part and make the pony low, it can look very modern and fashionable if done well. Or, just pull back the top section of your hair and use bobby pins, lightly tease for a little poof.
One of my favorite youtube channels on hairstyling and make-up how to tips is Michelle Phan here:
http://www.youtube.com/watch?v=lBAJJyJZdTM
these are some styles I'm thinking of:
http://media.onsugar.com/files/2010/12/49/3/1141/11414052...
http://www.hair2009.info/2009-medium-hairstyle-textured-r...