PT doesn´t need to to have dual winding, a single secondary is enough, so the divider goes simply between 12 and 0 taps.
The CT is ok like that, only I would add another divider to it so that you have some option to trim the total gain.
On the output you might want come RC filter to get the average value of the output, this could depends on what meter you are using.
2x18V transformer is overkill, since the rectified voltage will be 18*1,414=25V, so a 2x15V transformer will be enough.
Add a connecttion from pins 2 and 4 to the supply ground.