Is the marriage contract considered valid if concluded at home by the marriage official (Ma`zon)?

Yes, it is valid as long as it is registered at the court.

Is a Muslim is Permitted to Pray Wearing Shoes?

All perfect praise be to Allah The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions                                                                                                                                                                                                                                There is no harm for a Muslim to pray wearing shoes or slippers so long as they are pure, since a man asked Anas Ibn Malik: "Did the Prophet (PBUH) use to offer the prayers with his shoes on?" He said: "Yes." Moreover, Ibn Rajab (May Allah have mercy on his soul) said: "Performing prayer wearing slippers/shoes is permissible according the majority of the Muslim scholars." [Fatih Al-Bary,vol.2/pp.274]. And Allah Knows Best.

What is the monetary value for the expiation of an oath (Kaffarat al-Yamin)?

I`m a pious Muslim woman, but my husband isn`t, what should I do?

You should exercise patience, make supplication that Allah guides him to the straight path, and keep advising him kindly.