Don't worry.
If I convert, 300 pg/mL is 1101.3 pmol/mL in the international system, which, while not dangerous, are in the highest normal ranges for women. So a reduction wouldn't be a catastrophe.
Your endo is a bit conservative with his maximum of 200 pg/mL = 734.2 pmol/mL, but it's still well in the values that should allow feminisation, albeit maybe a little slower. But you know, sometimes, gradual is better and safer. If he went down to 100, that would be worrying, but 200 is fine. If I were him, I'd aim for 200, maybe a little higher, instead of setting it as a maximum, but: 1. I'm no endo and 2. I don't know your exact age, but you don't handle a 40-year-old like you do a 20-year-old, so perhaps it's all perfect.
As for your testosterone, don't even start to worry. Your levels right now, at 4 ng/dL = 0.14 pmol/L, are abyssally low. Lower than the lowest value of recommended range for women, 0.3 pmol/L. A reduction in your antiandrogen probably won't bring that anywhere higher than the recommended value for women, and will just reduce the amount of medication going through your system, which is good.
Unless your endo is way too aggressive with the estradiol reduction and brings your levels way below what he said, don't worry, much less cry. If effects are stalled, and they shouldn't, it's probably not impossible to increase the dose a little again.
PS: And gosh, US, change your units to the ones the rest of the world uses already! T_T