oh OP, I feel for you! I have numerous friends in this situation and it is terrible to be away from your country and your family when your relationship breaks down.
The one thing I can reassure you about is if you decide to leave in-between the two countries (long stretches in both) it can work very well, we do it with our kids (mostly for work reasons, but we also have immediate family in two different continents) spending about half and half of our time in (mainly) two places.
We have done this even through school years (homeschooling for half the year). The kids are not at all upset by it, in fact, they love it, and have a strong identification with both of our main residences (they are also perfectly bilingual and learning another two languages). It is tiring for us though!
However, we have done this with the full support of our kids' school and not all schools would support it, and we are worried about what might happen when the kids are at high school, in that, I don't think we will still be able to do it then.
We also own houses in both countries, so moving is easier and kids have toys, clothes, bikes etc. in both and have the stability of returning to familiar places, and we have also family and friends in both.
Done this way, for the kids it is their normal, not destabilising in any sense.
This said, I don't know that I would take my child away from a loving father, it is one of her fundamental relationships, also, you say he is selfish, and yet he is willing to allow you to go back? it's a huge sacrifice for him! But maybe if your DD would have better opportunities here, and you would be much happier and you can facilitate a close relationship maybe it is worth it overall?
On the other hand, I am gobsmacked at people advising you to just take your DD, even without the father's consent, what a horrible thing to do to a parent! Not to mention illegal!