1. I've imported my database into a DDT profile.  I'm assuming that from this point on any changes I make to the database schema in my development environment should also be made in the DDT profile.  Is it best to try and keep the 2 insync manually or would it be better to make the changes to the DDT profile, create an installation package and deploy it to my development environment?

2. It appears the DDT can't create Logins at the database server level or Users at the database level or am I missing something.  It appears the only security it handles is for Microfour's Role-based Security tool.  

The Browse service has to be running in order to "see" a SQL Server instance.  If you type in the name directly, and the server is there, then it will work.  The other thing that I have seen get in the way before is a firewall.  But I would imagine that you are dealing with the first scenario.