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Are you changing anything when you try to focus at night? Apart from your exposure settings, I would have thought if you can focus on something 1km away during the day, then that position should also focus on stars at night. I notice you have an eyepiece in your T adapter. Do you plan to do some planetary work? If you just want to shoot DSOs then it's best to remove it unless you have some amazing tracking setup.Once you introduce an eyepiece into the ootical chain, your effective f ratio rises sharply and the amount of light that reaches your sensor is reduced.
The fact you can focus during the day and not at night could simply be because you can see the image a lot brighter as apposed to the darkness of the night sky. Try to get focus on the moon, it's bright and big, much easier than trying to focus on a star. Use liveview rather than the optical yiewfinder of your camera, that way not only can you focus more easily but you can change the camera settings to make the object you're focussing on bright enough to see.
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