How to export all the security-related information from a SQL Server database

I'm sorry you haven't had a response since yesterday; here's at least a starting point for you.

You can try pulling the pieces you need out of. As always, read the discussion threads (I was, regrettably, unable to find a script endorsed by the big names I recognize, so test thoroughly! Schema, object, server, and column level permissions are often missing).

I haven't actually used any of these, but they're a set of starting points, in no particular order.

List all permission in all databases

Automated Permissions Auditing With Powershell and T-SQL: Part 1

Permission scripting over all databases

Script DB Level Permissions v2.1

Stored procedure to script out user permissions

Security Queries: Database-level

Security Queries: Server-level

Idera SQL Permissions Extractor seems to be the product you're looking for.

It can script server and object permissions and it is free. There is also a commercial edition, called SQL Secure which has more features.

The feature comparison between the two editions can be found here.