Thank you for your pictures and questions. I think that based on the photo, you are a good candidate for breast augmentation surgery. As for volume, you should try on implants in your surgeon's office to determine if 290 cc gives you the volume you are looking for. If so, then your surgeon can choose an implant in that range that fits your frame. I would say that in patients that are petite such as yourself, a round implant gives a very rounded appearance and a rounded upper pole of the breast, which I would not consider to be "natural." Not to say that this look is bad, it is just not natural. So you need to ask yourself if you want a rounded full upper pole of your breast, or you really would rather have a more natural result. If you are more interested in a natural sloping upper pole, you may want to discuss with your surgeon the use of teardrop form stable implants. As for the distance between the implants, your anatomy defines that, not the implant. If you have a wide sternum with outward pointing nipples, that result will not change, and might even be made more prominent with placement of implants and that is something you need to expect and accept before proceeding with surgery.
Hope this helps!