What is the expiation for being forced to give a false testimony in order to achieve reform?
Achieving reform is done by following the way of Allah through giving back rights to whom they belong. Therefore, repenting to Allah from false testimony is only achieved by abrogating it, and the person in question should expiate for that oath if he had taken it, so that Allah may forgive him.
Is it permissible for me to name my newborn baby boy “Al-Moustafa” ?
There is no harm in naming your son “Moustafa” without using the ”Al”.
Is it permissible for a woman to say that she loves her husband more than her father?
It is impermissible for her to say so since this would hurt her father deep down. Allah, The Almighty, Says in this regard (What means): "And that ye be kind to parents." [Al-Isra/23]. Saying such a thing to her father isn`t an act of kindness since she should keep it to herself even if she felt that way.
Is a wife considered sinful if she asked for divorce because her husband married another woman?
A second marriage is lawful, and so it is impermissible for you to ask for divorce because of that. If you are certain that you won`t be able to deliver Allah`s rights and those of your husband`s , then it is permissible for you to ask for Khul`a (Divorce on the demand of the wife). However, you should exercise patience since after difficulties, there is easiness by the will of Allah.