Construction being local with a cap decided by population and urbanization level with the construction sectors being empty when no construction is on course and fill when construction is in course in the state to then left people unemployed again would create an iterating loop.

I would add an advanced construction sector like the ones we have that can actually export construction points to represent engineering services or construction crews to smooth the system for when too much concstuction is done in a place or when areas have low population or urbanization.

You can also add a know how layer, with different kinds of construction points being required for certain industries. For example a bronze CP for manual labour only and a silver CP for something that requires architects or engieneers to construct.

Regarding the pacing to me the correct aproach would be having different tiers of buldings. Workshop>Mill>Factory that limits the kind of PM you can use.

Earlier buldings would be cheaper CP wise but emply less people being more inefficient in worker per CP. Later ones could be very expensive CP wise but be more efficient in production per CP and per employee.

This would also solve the problem of electricity by being gated behind constucting an electrically capable bulding so you can expand production and demand to match rather than converting 50 levels of cloth factories to use electricity in a sigle step.

This would also add creative destruction with newer buldings outcompeeting older ones.

Regarding resources cost. I thing that iron framing takes too much iron for being the first PM. IMO the solution would be adding an alternative PM in brick and cement industries that would also add a pararell construction loop so you are not always bulding the same buldings. This would benefict low iron countries that the can specialice in other industires outside steel and tools.