I don't think you will have to wait much longer to see roots. As they have stayed green and healthy for 6 days, I would expect to see roots in the next week. My shortest time to date is 8 days and longest 14.

As for your 3 other questions, I am going to kinda dodge them. Because like a lot of techniques, everyone seems to have their own methods that work for them.

I mist once a day everyday till I see a root and start to open up the vents after about 4/5 days.
The 24/0 20/4 18/6 debate will probably go on forever. I have no idea which is best, I just know that 18/6 is the cheapest.