It would be nice to know the exact formula, but atm I am grabbing at any bit of info on the relation between colony cost->population->manufacturing->economy and everything in between.

I understand the basics, colony cost determine your max population, which determine your manufacturing capabilities and wealth production through trade. But all the intricacies allude me 

Your workforce is divided into Agriculture/Environmental + Service Sector + Manufacturing = 100%. Manufacturing are the people you get to use for stuff like factories or research labs or mines.

As mentioned, Agriculture/Environmental scales with Colony Cost - it bottoms out at 5%, and goes up by 2.5% or something per 1 Colony Cost.

Service sector percentage scales with population. I think it's at about 400-500 million where it caps out at 75% of your population. I'm not sure the exact formula is known, since the last posts were a long time ago and it may have changed.

It's because of the way that service sector scaling works that moving people off of Earth is so useful - if you have 1 million spare workers on Earth, you can pick up 4 million people and drop them on colony and have 3 million available workers. It's worth it to move people off of Earth to a developing colony on an Ideal Habitable World until you hit 250M people or so. At that point you're not gaining much in terms of lower service sector needs.

EDIT: For Trade, supply and demand scale with population. Each world produces surpluses in different things. There are breakpoints at which colonies begin to demand specific goods, and I think it's 10M and 25M. A colony of size 1M only wants a fraction of the trade goods, a colony of size 11 million has demand for most of the trade goods, and a colony of size 26 million wants some of every type of trade good. So for ideal trade, you want multiple 25M+ worlds that specialize in different things so they can trade between them.

Steve used to post the exact formulas for stuff like this, it's probably buried in mechanics.
But for the wiki it should be fine just to state what effect it has, I might just check what population levels cause various levels of service industry similar to how I checked how much infrastructure is produced by population levels.

The wiki mentions that agriculture starts at 5% and goes up with colony cost. I believe it's a multiplier, 10% for colony cost 2 etc.
Then there's service industry which grows up towards 25% or something by the time a population reaches a certain level.

Venus as a colony is a daunting proposition unless you use orbital habitats or have a humongous amount of terraformers. Better left to automines.

You should always keep a close eye on the colony cost before settling a planet. Realistically, anything about 4 is very inconvenient until you start terraforming.  Over 6-7 is not worth considering without terraforming.

Theoretically you could strip the planet of infrastructure, and/or moving back the population with colony ships. However your civilians will keep growing it, no matter what you do. You might simply want to abandon the colony, I don't think it's a battle you can win unless you have a lot of colony ships/freighters.

What you could do if you really want to is make civilian contracts to move away, for example to earth or another place you want to colonize, all the infrastructure. But even in this case I' not sure you'd manage to overrun the civilians who keep growing the colony.

At some point or another you will be forced to abandon the colony...

Unfortunately venus is so hostile the entire population will be working on "agriculture" to support itself. Terraforming is the only option and it could take decades of massive investment considering how thick it's atmosphere is.
Orbital habitats do have a fixed manufacturing percentage and are the only useful way to colonise venus at the start.
As I recall every increase of 1 in colony cost requires 5% more of agriculture workers. I could be wrong on that number though.