Q1:

Is there any way to change the user information through the API? Can you change the user passwords through the API?

A1:

You can use the CommunityServer.Components.User class to edit the properties of the user. There is the User.Password property and User.ResetPassword() method.

Q2:

Is there any way to make the Forum module more content oriented, for instance break down posts into content items viewable/editable from within Sitecore?

A2:

The Content of the Forum module is contained in the Forum module database. You can manage Forum module Permissions for the forums.

Q3:

Does the API have methods to retrieve the forum information such as the list of all of the messages in the forum or users/messages posted by a certain user?

A3:

Please use the classes from the CommunityServer.Discussions.Components namespace of the CommunityServer.Discussions.dll assembly.