Locking down individual nodes for editing by a single user?

I have some specific permissions requirements for a project I'm working on, and I'm trying to address them with this module. Can anyone tell me if there's a way to accomplish this?

The requirements are these:
1) Certain content types may be viewed by anyone, but edited only by administrators
2) Other content types may be viewed by anyone, but edited only by authenticated users
3) Still other content types may be viewed and edited only by the user that created the content items in that type
4) In the case of #2, there will be special instances where a given piece of content will need to be locked down and editable only by a given user. This will be a 1-1 relationship in most cases, but there can be hundreds, perhaps eventually thousands, of relationships.

The Content Access module has gotten me most of the way to where I need to be. Everything except #4 is covered. Then I tried installing nodeaccess (not to be confused with node_access, the distinction between which was making me cross-eyed), because it looked tailor-made to take care of #4. However, I couldn't get the permissions tab to show up on the content items no matter what I tried, and there's no documentation that I could find, so I ditched the approach and uninstalled the module.

Then I thought that I might be able to emulate the per-user access functions of nodeaccess in Content Access by creating a new role (let's call it "content editor"), enabling per node access control settings on the content type, setting the content editor role to edit own content and removing all other content editing permissions on the node. Then I'd just assign the user in question to the content editor role and change the authoring on the node to make that user the author. I was feeling pretty proud of myself for that one, until I realized that you could only add permissions on the access control tab of the node itself, not take any away. All existing permissions for the content type are grayed out and uneditable.

So, that puts me back to having 1, 2, and 3 taken care of and no solution for 4. Does anyone have any advice on how I might be able to get 4 in place while still preserving the other three?

Any and all advice will be greatly appreciated!