Hi
I think the first part of your question is much easier, when we know the current distribution we can predict the antenna pattern by integral methods represented in text books of electromagnetism. Also you can use numerical methods for complicated structures. But the second is very different. You can not change the current distribution easily because you can not obtain the desired amplitudes where you need.
I'm interested in the topic too, and any explanation specially related to the second part will be appreciated.
With best regards.