If you checking the level of coolant when car is hot then every time you looking you might see a different level. The checking process must be with cold engine.
But in case you see the coolant level below the min when car is still hot then you have for sure problem with leakage.

To check the actual level of engine coolant the car must be cold like the morning.
The reserve coolant box has a bad cap that at road bumps let the coolant in little amount to leakage.
The second reason for leakage is the packing rubber ring of radiator.

Did you rebuild the axle?
It seems that shaft is putted wrong between the joints.

To make the same thing as ASR is difficult issue because we don't know the dimensions.

The rotors of some mb with thickness of 23mm and diameter of 259mm don't fit to civic ej9 because the stud pattern is 4x114.3 and our civics ej9 have 4x100.
The best choice is to upgrade the brakes to MGZS 160 with 4studs and 282mm rotors.

For d14 engines we don't need bigger throttle bodies because the bigger tb has a negative effect to the air flow, actually the bigger tb reduce the air speed that coming to the plenum. The result is obvious the power of is reduced. I have a query, is the d16z6 intake manifolds same with d15b7 and d1...