All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
There are several points which we would like to clarify to you:
Firstly: if this gold was kept for personal use, even if you wear it once a year only, then it is not liable for zakaah according to the majority of the scholars. However, if it is intended for savings and not for use, then it is liable for zakaah. If it is liable for zakaah, then zakaah is due after the lapse of each lunar (Hijri) year. As for the stolen gold, if it was stolen after the lapse of a full lunar year in your possession, then zakaah is due on it and it is not waived because of the theft. But if it was stolen before the lapse of a lunar year, it is not liable for zakaah.
You are required to pay zakaah at a rate of one-quarter of one-tenth (2.5 %) of the gold or its monetary value. You should calculate all the gold liable for zakaah, i.e. all that reached the Nisaab (the minimum amount liable for zakaah) after the passage of a lunar year; divide it by forty; and pay that result as zakaah in kind or in cash (gold or its value in monetary value) ,as mentioned above.
Secondly: neither you nor your husband bear a sin for looking for the thief and reporting the theft to the authorities. But since your husband preferred to please his father by not reporting it, he is praised for it and will be rewarded for it, Allah willing. He did well by choosing the Hereafter over the worldly life and giving precedence to obtaining his parents' pleasure over any worldly gains. You also did well by obeying your husband and helping him in this regard.
Thirdly: we advise you to forgive and pardon those who wronged you and meet their evil with kindness; Allah, the Exalted, will replace their enmity with friendship and their hatred with affection. He says (what means): {Repel (evil) by that (deed) which is better, and thereupon the one whom between you and him is enmity (will become) as though he was a devoted friend.} [Quran 41:34] Moreover, the Prophet, sallallahu ‘alayhi wa sallam, said, "Verily, Allah increases the one who forgives in honor." [Muslim] So adorn yourself with pardoning and forgive those who insulted you so that you attain honor in this worldly life and in the Hereafter.
Fourthly: you bear no sin for not meeting your mother-in-law or not receiving her. However, it is better for you to let go of the past and turn over a new leaf with them, one filled with pardon and forgiveness, hoping thereby to win the pleasure of Allah first, and then your husband's pleasure. You should turn to Allah and frequently ask Him to relieve your distress and help you adhere to His obedience.
Fifthly: you should expect the reward from Allah for every calamity that befalls you, and know that when the believer endures the adversities that befall him or his wealth with patience while expecting the rewards of Allah, he earns great rewards as a result. Allah, the Exalted, says (what means): {And give glad tidings to those who are patient; who, when disaster strikes them, say, "Indeed we belong to Allah, and indeed to Him we will return." Those are the ones upon whom are blessings from their Lord and mercy. And it is those who are the (rightly) guided.} [Quran 2:156-157]
For more benefit, please refer to fatwa 83577.
We ask Allah to reward you generously and compensate you with what is better.
Allah knows best.