Most of the questions you are asking are somewhat unknown in the Bedrock engine. Right now it seems as though we have somewhat broken villages and villagers, that don't seem to follow the rules that the PC java counterpart does.
Villager max population is supposed to max out at 30% of the total number of valid village houses that make up a village, but clearly this is not the case, in many of my tests they breed well past the 30% mark. In one case I have 24 doors, with a max population of around 20 to 30 villagers.
Villagers are supposed to have a 20 minute cool down time before they can breed again, but this is not the case, right now villagers can breed within a minute or two after creating a baby.
Villagers are supposed to have a 3 to 5 minute cool down in any case of negative popularity to the village. That is to say that if anything effects the village popularity in the negative, such as killing an iron golem, or any villager, regardless or not it was done by a player, but so long as a player is within the villages range, then a 3 to 5 minute cool down is imposed, which is supposed to prevent any breeding. This is also not in bedrock engine.
As for villager door detection, I believe it is the same as the PC java counterpart, which is + or - 16 along the x and z axis, and + - 2 along the y axis.
I'm not entirely sure if your asking questions for a village trading center or an iron golem farm, so I won't discuss anything further.
So I've actually just built an Iron Golem farm. What I have done previously to grow my village is a simple set of buildings with 40 doors. Normally, with the 30% max cap, this build yields ~12 villagers. However, on Bedrock this is definitely not the case. After a very short time, I'm now up to 5 Iron golems, and probably somewhere around 30-40 villagers ( I can't keep track of the exact number, but there are a ton of them!). After sending off some villagers for the Iron Golem Farm, they just continue to reproduce as usual.
I agree with Cire360, a majority of the villager mechanics are still sound, but their cooldowns and rate of breeding is definitely broken at this time.
As a side note, I also noticed that you can't suffocate Iron Golems, ie. with a piston pushing a block into them. They take no damage. Super weird.