Q:

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?

A:

Does adding more villagers, doors, or space increase the spawn rate?
No. From the Minecraft wiki on Gamepedia:

The chance of spawning is 1 in 7000 per game tick

Adding more villagers, doors, or space does not change this fact. If you want more golems, you need more villages.
How close can I place my villages? 
Again, from the wiki:

If their centers are to share the same x & y or y & z coordinate then the remaining coordinate must differ by 66 or more.

How do I determine where the center is?

Upon creation, a village center is defined as the geometric barycenter of the active doors' locations

In summary, the most efficient design is to create a cluster of villages whose centers are spaced exactly 66 blocks apart (on any single axis). Each village must have at least 10 or more villagers.
You can extract tips and tricks from many tried and true designs here.

