Wrote

However the middle equation becomes unreadable as soon as we have values that are not round numbers, so we also need to control the format of the values of variables in the middle equation, and to insert some "=" in-between.

This is much beyond my ability!

Numerical computations of functions are inexact as explained in Mathematica.
ReDef was explored by Tom ... so many caveats, in short: useless IMHO.