Eggs are ready, have a few questions

[trsers]

Okay, this is my first time hatching chicks with an incubator. I know some of these questions could probably be answered if I searched the boards long enough, but it gets frustrating for me.
So here goes...
I have a tiny flock of 4 buff orpington's 3 hens and a rooster. The rooster is turning mean on my kids and has got to go. He's being picked up on Saturday. In the meantime, I've been saving eggs to put in the incubator. I have 12 right now. I want to add 6 more hens to the flock. So here are the questions.
1. With only 3 hens, is there a good chance that all 12 eggs will be fertile? The rooster seems to chase the ladies often enough, but I don't know how often is enough.
2. With 12 eggs, I am counting on some not hatching and some turning out to be roosters. I want 6 hens, but will make do if I get 4. Are my chances good with 12 eggs, or should I incubate more than that?
3. I have read everything I could about hatching eggs this way, but once we get rid of the rooster, I won't have fertile eggs to try again (unless I mail order). In your opinion what is the very most important thing I have to know about this process?

Thanks for all your help! Tara

 

[katrinag]

I would tend to say yess that all the eggs are fertile.
I would incubate more like 18-24 eggs. You can always get rid of the ones you do not want.
Eggs can be fertile for up to 3 weeks after the roo is taken out of the flock.