Those regions are full of poor farmers, no point in taxing anyone there. Only when you start building up the industry and getting tax/bureaucracy innovations, when your industry can keep up with the resource requirements, when the SoL rises, only then it'll become manageable.
I play Qing a lot, so I have a bit of experience with having numerous 20-30M pop provinces. It takes a while to get things up and running, so don't think you'll have it done by the 1850's. The 1870's are more realistic target for that.
And yes, it means you'll have 50-60 administration buildings in those provinces, sometimes more. No way around it, if you want 100% taxation at some point. The amount of paper you'll need, and money to pay for all those government employees, requires a certain degree of wealth and resources on your part. You have immense requirements, so you have to make sure that everyone is in the workforce and has a good taxable income first, else the taxes won't pay for the taxation system.