Is taking all the furniture from the shared home after divorcing one's wife, based on family advice, considered theft, and how can one atone for this act, and does it affect the validity of the obligatory Hajj?

Whoever intends to perform Hajj or Umrah (definition) must ensure their money is lawful and rectify any injustices. A divorced man must pay his ex-wife her full dowry. If the household furniture was not part of the dowry, then each spouse owns what they purchased with their own money. If they shared the cost, then each has a share commensurate with what they paid. Therefore, the questioner must repent, return to his ex-wife the right he usurped from her, and seek her forgiveness.