There is a number of ways to create and change models in OpenSCAD. The differences are very important.
The most straightforward way is to create a Constructive Solid Geometry (CSG) design, without any additional templates or libraries. Most models are not created this way though.
Most models use libraries such BOSL2, they import models which are designed in FreeCAD and exported to OpenSCAD. The resulting models going to be dependent on various sources, there is not going to be a single SCAD script file but several. Keeping the models updated, and changing them going to take more than just changing a few parameters.
This thread is used to discuss ways to categorize the designs from the simplest using a single script file to the most complex - using multiple source files, PNG files, exports and imports.
This is not a place to ask for help with you model files, this is a place to design your project and the models in the project.