Here's the answers to your questions:
1 - Yes, but since our new admin is almost done we'll probably have official settings for this in the near future.
2 - No, all affiliate links will remain the same and keep working. No need for updates.
3 - Yes, that's correct to create a year-long cookie. You can see in your post that the browser interprets only the first part as a whole link, entering a space and then a number keeps that number value separate and our system will be able to understand it.
4 - Unfortunately there is no way for this to work backwards. A cookie can only have the settings it was created with, we cannot remotely access them to update them if you make a change in your account.
5 - Yes, if you plan to use product specific settings be sure to enter the cookie length in them as well
6 - Yes, that is the correct place to enter your landing page URL.