The game is saving to the cloud so having it connected is good. Reason I asked is because it having two devices with the same game often gives issues with cloud saving. Which could be caused by an unstable internet connect. I highly doubt your account was hacked. I think the save to the cloud didn't go smoothly and got messed up due to it.
In this case, with my limited knowledge of what EA can actually do I would think going back to a previous save point would solve the issue.
Has EA suggested reverting back to a previous save point? If it hasn't I'd suggest asking EA specifically what the closest save they have for you before the problem occurred would be, and revert back to that if possible. You might have to do the baby quest again, which isn't fun, but would solve the current issue with a "broken" baby. And hopefully prevent this issue from coming back in the future.