Powertheft is not common here. It happens in criminal circuits here that people bypass or stop their powermeter so they use more as they pay. Power comes in under ground here and ends in a panel with a sealed powermeter. Once a year they come by and registrate the powermeter readings. So it is very difficult to steal power from someone else. (it is possible but very hard to do). A power theft meter is also allmost impossible to mount over here.
A friend of mine travels a lot for his company and they have a very big factory in India, he told me some horror storys, and showed pictures of your electric system. It sounded very dangerous. The very high power input of that factory was in a leaking building, covered with some plastic foil. If it rained to hard the system would shut down because it get flooded and then they send some poor guy, barefoot through the water to power it on a again and were supprised he ends up in the hospital. They (the workers in the factory) had no clue about the dangers.
I have no problem with the idea of a power theft detector. If it is handy in your country why not. But I think this is not a project for a person with very little knowledge of electronic basics. It is very dangerous. We have 16A or more coming in to our house. The safest way to measure that is a transformer like used in a current clamp meter. A torroid you mount around one of the wires. Measure it with a TRMS converter that can handle the distortion on the line, scale it and read it. Then you have current, you know the Voltage and then your microprocessor can calculate the power. But he still thinks he can use something stupid as a 10 Ohm 30W resistor after several formulas and examples how to calculate this and still has no clue about how to measure that voltdrop because he does not read or understand the solutions.
I could draw a schematic how to do this. It is not difficult for me, I just m,ade something like that to measure current after my isolation transformer and variac. But that is just to feed one DUT, not a whole house. I think measuring the power of a whole house is not a project for people who do not know a lot about electronics because of the dangers.