Yes
No
Yes
Yes
Yes
Yes
No
The groom's father is expected to wear formal clothing to the wedding.
Only if it's a formal wedding.
Yes, if it's a formal wedding - it is a way to respect the bride and groom. But if the wedding venue is based on beach areas you can consider beach wedding dresses that might better to show your appearance.
Generally, the accepted language for a wedding invitation is formal. If the wedding is going to be less formal, then the invitations should follow that example.
"Those attending Kim's wedding must wear formal clothing."
Depends on how formal the wedding is and the color of the suit you are wearing.