Axélle: Your E is inside the range of a pre-menopause woman, so it is a fine range. You are also post op, so your T should be very low! It is a good combination for development.
Post-menopausal women don't have breast development because their puberty is already gone and through for a long time. You, from what I understand, began the development of feminine sexual characteristics fairly late on, because of transition and everything, so it is possible you will still have breast growth. The Endocrine Society recomends E levels of about 200 for women in transition as ideal. As you in the laboratorial test, there is a huge hormonal range for females, so even if yours ins't 200 spot on, 259 is fine as well.
739 would be an excessive amount. It could give you adverse effects and actually not be effective into bringing your desired physical changes at all.