Have you engaged directly with our Higher Education user group? Higher Education is the location for that group and participating in that group might provide you some great resources.
I am going to try and provide some information to get you started on the rquests above.
These will be great resources for moving forward with scaling out to more users.
2 & 3.
One way I would attempt to maintain some sort of order in the Tableau Server is to maintain permission groups for the users. If you limit the a specific group of people to be the publishers you wil be able to maintain some security of the data as well as cleanliness of the Tableau Server. i.e. Only clean and tailored data sources will be published.
4. With any server, site, data storage, or computer network. A process for maintaing a healthy environment is key. Removing old data sources and workbooks is a great thing to build into the process of the people using the Tableau Server. Self-policing is always a preferred method as this eases the amount of work for the admins as well as the user is best to know when they no longer need a source. Though having some sort of aging policy would probably be best as running your server low on disk space can cause performance issues.
5. By space limitations do you mean the size of the site/ project?
6. I have not personally done much on the procurement side of things.
Hope some of this is useful!