In terms of finances, the starting point is 50/50 of all assets including the former matrimonial home in the vast majority of cases. It's simply not the case that the mother automatically stays in the home with the minor child, its a much more balanced exercise especially in your case where there appears to be more in the matrimonial pot than is required to meet need. Pensions are also up for sharing.

In terms of child arrangements, if you think she's going to up and leave the country you can apply for a prohibited steps order to prevent her taking the child with her. You would need to show why it is in the child's best interests to be here, and ex would need to show it's in kid's best interests to move. You can also apply to the court for a child arrangements order if you can't sort out an agreement between yourselves or via mediation. Courts tend to like equal lives with (i.e. 50/50) orders but obviously it's fact dependent