I'm a ddd bra size. should i get the 1xl or 2xl?

if you are that large-busted, I'd suggest at least a 2XL - this runs small and tight - with NO wiggle room

I wear size 16/18. What size should I purchase?

I learned through mistake a size medium in Chinese size i had purchased was way too tight it fitted like an extra small when I bought this item from the seller i ordered another med but it was us sizing it fit perfect and i love the jacket its true to size the only thing I can say is make sure you specify us sizing

Is the zipper bottom removable?

Yes zipper bottom is removable.. I love the jacket..love love love

Have the size issues been fixed? I bought this a few years ago and at 5'4" 150lb my arms simply have too much muscle to fit in the medium.

i was curious the size as well im usually 12/14 i order a xxl and it was way way to big i have to go 2 sizes down so im guessing they fixed that problem