With a few exceptions, your condition with the calcifications sounds quite similar to my own. I've had both the surgical (excisional) biopsy and the stereotactic (needle) biopsy of microcalcification in my right breast within the past 3 years. And, like you, I have dense fibrous breast tissue aka Firocysistic Disease of the breasts.
According to my family physician, 30% of the female population has some form of fibrous breast density so, it is not at all uncommon. But, it's a condition that makes the interpretation of a mammogram more challenging. As for the microcalcifications, the surgeon who performed my surgical biopsy told me that they are rarely, if ever, found to of a cancerous nature. They are, however, an abnormality and their appearance may indicate that something is amiss within the surrounding breast tissue, thereby... triggering the growth where the calcifications appear.
In answer to you questions, I would say that the development of these calcifications is unrelated to breast feeding (I never had children; and I have them). As for breast fondling... well, it's certainly an interesting theory to contemplate; but, I seriously doubt that could cause the calcification growths. And, as for the size of the cluster, doctors do look to see how these clusters form when they make their analysis.
Now, the fact that your mother had Breast Cancer is, indeed, considered to be one of many risk factors. And, doctors will definitely take note of that.
I have 2 aunts on my mother's side who had Breast Cancer plus, my sister had Ovarian Cancer... the radiologist who oversaw my stereotactic biopsy considered that to be rather significant.
But, if I were you, I wouldn't jump to any conclusions about the nature of the calcifications. I spent many sleepless nights doing that... second guessing, wondering, worrying and scaring myself.
The biopsy results will tell you the nature of what you have.
By the way, my biopsy results returned with benign findings, both times. I'm hoping that your results will return favorably as well. Good luck!
You have no doubt already seen the Surgeon so this answer may be rather useless but here goes. Microcalcifications are an indication tht the breast is reacting to some abnormality wihin the breast tissue. They would not be due to the two things you mentioned. Scattered about these calcifications are of no particular cause for concern but when they are found clustered or in certain patterns then a biopsy is usually recommended to determine the cause. Regards ....