Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
The right of parents in Islam is great, and being kind and dutiful to them are acts by which a person gets nearer to Allah. The best act of kindness and being dutiful to one's parents is to be a means of saving them from shirk and every thing that leads to it. Your husband has to do his best to convince his parents to give up wearing these amulets especially if they contain anything that is not Quran.
The prophet said. "Incantations, amulets and Tawla are shirk" Tawla is something that the jugglers use claiming that it make the man love his wife or the opposite." Reported by Abu Dawud.
You have to help your husband in carrying out this mission (duty).
As regards the issue of residing with your husband's parents if they ask this, then you do not have to refuse them, as your husband has to obey his parents if he is able to do so and is not harmed by doing so and if there is no great hardship in that.
Imam Muslim reported in his Hadith that Abdullah Ibn Omar said: "A man came to the Prophet (Sallallahu Alaihi wa Sallam), asking him permission to go for Jihad, so the Prophet (Sallallahu Alaihi wa Sallam) asked him "Are your parents alive?" The man replied "yes". So the Prophet (Sallallahu Alaihi wa Sallam) told him: "Make Jihad in your parents."
Besides Abu Dawud reported that Abu Saeed Al-Khudri may Allah be pleased with him, said that a man made migration to the prophet from
So if a man is ordered to stay with his parents unless they give him permission to make Jihad, then it is more appropriate for him to obey them in other matters.
However, it is forbidden for your husband to obey his parents in wearing amulets or doing any other act of disobedience.
Allah knows best.