If I were to set villages on slow speed and leave them be for 6-8 hours, if food wasnt a problem would they be ok?

I wouldn't recomend it. It's not just the food, they could get sick as well. I always pause the game when I leave it in the beginning. But that's up to you to take that chance. But hey! good luck and have fun with it.

well I need a lot of tech pts and will lose interest in the time it takes to accumulate them. If I have a master doctor, he will treat the sick on his own correct? How about an adept doctor?

As long as food is unlimited and you have some young (under 20) farmers, doctors, and breeders, and your population is fairly big, they do survive on their own.

There are two ways you can prevent accidental tribe die-outs.

(1) Make a backup of your game before you leave. *Recommended*

(2) If you come back to a dead tribe, quickly start Task Manager and End the Virtual Villagers process. This will exit the game and make it think you never started it. Time travel back a few hours and see if they're okay. If so, put them on pause and put your clock back to normal.