welcome to HCM!
a big fibroid
with excessive bleeding,
with history of cancer breast.
my advice will be-hysterectomy.
wish u all the best!

Thanks for your question. The presentation you describe is certainly a difficult one. The obvious answer is to have a hysterectomy for abnormal bleeding associated with the fibroid. There is a concern of malignancy in fibroids that grow rapidly, called leiomyosarcoma; yet this is a very rare form of uterine cancer.
Fibroids are estrogen dependent so giving estrogen to a woman with a fibroid can make the fibroid larger. The IUD approach is a reasonable approach. However, having an irregular cavity within the uterus makes the insertion difficult and may contribute to increased cramping. The risk of perforation is higher with a misshapen uterine cavity as you stated. A vaginal ultrasound would confirm if the IUD is in proper position and rule out perforation.
At age 51, you are close to the onset of natural menopause, which would probably alleviate the bleeding problem and the reduction in estrogen at menopause usually shrinks the fibroid.
My approach to this situation would be to perform an office hysteroscopy with visually guided endometrial biopsy to rule out cancer, polys, or precancerous growths. You don't mention if you had a biopsy after the onset of your heavier bleeding episodes. It would be a mistake to assume that the bleeding is merely from the fibroid and miss a more serious reason for the bleeding such as uterine cancer.
If visually guided biopsy is negative for cancer, there are two approaches that could be tried, with costs of each needing to be taken into account.
The least expensive option would be to place you on a high dose synthetic progestin (norethindrone acetate or medroxyprogesterone acetate) three times a day for 90 days. This is like having a continuous D&C with medication. Long acting Depo Provera injections are another possibility and not prohibitively expensive.
The most expensive approach would be Depot Lupron administration monthly. This would place you in a medically induced menopause that is reversible and is used to decrease the size of fibroids while planning removal of just the fibroid (called a myomectomy). A myomectomy is a consideration but would be just as expensive as hysterectomy so I would proceed with hysterectomy should you decide to have surgery. Lupron can reduce bone mass so a baseline bone density test is recommended followed by a post treatment bone density test. Lupron is approved for six months use by itself and for twelve months when a small dose of estrogen is given while taking this medication. The estrogen level is low enough to protect bones but not high enough to induce growth of the fibroid. Estrogen use and breast cancer risk is an entire discussion in itself, but if monitored, I believe that the benefits of estrogen treatment in menopause far outweigh the possible risks of breast cancer.
I hope this answer gives you some options to discuss with your gynecologist. However, I am available for follow up.