Question

if we use unspecified forces to keep a charge from moving for ease of calculation won't that bring in calculated value​

Answer 1

Coulomb's law allows us to find the force between two point charges. ... "There will be zero net electric force on the charge in the middle due to the other charges. Using Coulomb's law, the force due to the +Q charge is positive, and the force due to the -Q charge is negative.