[Aiken]

2 - Shields and armor protect only WP itself. Damage to WPs is applied to unit in stack, which is choosen randomly and shield points are not not a significant part in the formula. So heavy shielded WP will not attract hits to itself, it will be harder to destroy such platform - that's all. It's wiser to put some shield/armor to each platform instead.

3 - afaik yes.

4 - no, and see reply to Q #2.

Don't really understand Q #1.