All the best of luck for you! I suppose you guys are married now, so congratulations!
I'm partly in the same boat as you. Visa problems, paper work, etc etc and most of all, deciding the country where to live! For us it might also be a battle between UK and Japan, and also Finland lurking in the background...
But to be honest, for the child, I think Japan might be better. It's safer in Japan than in UK, and the mother can understand everything that concerns her and her baby.
I hope you don't mind, but that's why I felt uncomfortable in UK. It didn't feel safe. Country with many nice things, but for children Japan might still be a nicer place to be...and this is just my opinion - not a fact.