Lost, You actually answered your own question about signs of clarity. When they begin to do the "normal" things that they use to do, that is clarity. Acting more like himself is a sign of clarity.
How do you handle all of this? Treat him as you would a friend. Accept him as he is right now and just go w/the flow. No expectations or you will be disappointed when he pops back in the hole of depression.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
