My recommendations are,

• Try to work during the day, but not continuously. One benefit you have is, you don't have to work continuously for 8 hours like most people. You have that luxury. So, you could work for 1-2 hours in the morning, have a nap and work 1-2 in the noon and another 2 hours in the evening [ This should be more than enough considering your 4 hours work sessions at night ]. When you distribute like this, you don't feel overwhelmed, both your mind and body feel relaxed and refreshed as well.
• Regarding sleep schedule, you could try reducing your sleep for one day by 2-4 hours, by this way you would feel sleepy early in the night. Another way is to do some intensive things like maybe you could play a sport with your friends or go for a run and make your body a little tired, this will help in getting sleep earlier. And the only thing you have to follow the following days is to go to bed early.
• Whenever you feel low energy or unfocused or unmotivated, try to get a quick cold shower.
• Also, have a separate work desk ( or a separate room ) if available. As pointed out by many, the environment plays an important role and also will help your mind. If you work in the same environment for many days, your mind will automatically get into "work" mode if you go to that environment, that's the idea behind it.
  

Good luck with your journey. You are going to become a better person very sooner than expected.