How do I get focussed images with my T-adaptor and 6mm eyepeice?
Using the eyepiece, and no camera lens, is a very different configuration to the camera+tube+scope (case 3).  The configuration you're after is "Eyepiece projection".

I don't know exactly what you have available, but I believe you will need to fit a T-threaded extension tube to the external thread on your T-adapter. Then fit the camera onto that.

Note - before you go out and buy a new extension you can probably do a hand-held test of this by the following:


Attach the adapter to the scope, with a low-power eyepiece in the adapter (low power makes the test easier to see.)
Point the scope at anything distant (you can do this in daylight, but NOT at the sun of course!)
Now hold the camera, by hand, a few inches behind the
eyepiece+adapter. Perhaps you can use a cardboard tube to keep the stray light out.
See if you can adjust the scope's focus, and the camera position, to get a sharp image.


If this worked, then you can get a T-threaded extension tube to go on the back of your current adapter, to hold the camera in position.

See for example this link:
http://www.astronomysource.com/2011/10/13/eyepiece-projection/