"They say that what's not healed in 12 months becomes Chronic or life-long."

This is not a valid statement. There are lots of such statements about concussions. Many here on NT have seen fabulous improvements in their second or later years.

Duration of sleep and quality of sleep (REM sleep) both impact fatigue issues.

The light issue may just be what is called sundowning. It refers to later in the day after a routine number of hours have elapsed since the last sleep period. I bet that you would do better if you were getting better sleep.

What are you doing during those hours where you would usually be sleeping ?

How long before going to sleep do you start preparing to go to sleep ?