I think you should sleep right after you come from work. That way you will sleep until like lunch time and be able to seize the entire afternoon (get some sunlight) yes being able to get sun on your skin is very important, if you close yourself too much without seeing daylight you will start to get depressed very fast. And still being able to be up at noon when it's prime time for everyone. That's my tip for the schedule
Now other thing. I would strongly advise against a louder alarm clock. I had the fuckin loudest alarm clock ever when I went to uni and it resulted in me raging and turning it off every time and miss classes. Not good. Now I have a pretty normal mobile phone alarm (just make sure to set at least 2 different alarms if the 1st doesn't wake me up) and I get up every day in time.
About sleeping too much I can't help you, I have the opposite problem, I started working a few months ago and my main problem is sleeping too little, like 5 hours a day, which leaves me the entire day ruined. I really need to start getting some 7-8 sleep hours a day