I am really sorry to hear what has happened. It must also be more difficult if you are posted over seas as you say.
I have only seen two of my children once in two years and I feel it is purely down to Ex not helping the situation and full vegence on me leaving,(not for anyone else either). I took my Sol advice and went for a contact order which she has clearly broken. However, if I take her back to court she will again use this against me with the children so from a personal experience it is a waste of time.
I have so much advice from various sources and still very little contact, like you I do not know what to do next. The eldest changed her name to my Ex''
Maiden Name when she turned 16. The others tried to change their names at school also, again influences. But as I pointed out to the school who should know better they maybe wanting to be known by another name but legally they cannot change school reports etc until they reach 16. I got a letter of apology.
Sorry all about me at present. There is no real good advice as just keep trying I have not given up yet
Good luck and hope you get it sorted, like to hear if you do.