Games : Minecraft 1.8 - Iron golem farm questions on spawn rate and efficiency

So I've been building this thing, to see how it works and if I can increase the efficiency some:

Now, I tried to increase the number of floors, but it's hard to determine the effects of it. Some times it seems as though the whole thing is broke as well.

I have one pouch of villagers on either side, dont't know if that affects anything though.

So my questions to this design is:

Is this thing considered as one, larger village? Or two separate ones? How far away (vertically) does the next layer need to be for it to be recognized as two separate villages?

Here is the other one, which I have extended the length of:

And my questions to this design is:

Does increasing the space, doors and villagers increase the chance of iron golems spawning? Or does it just increase the cap?