Does building a house and meeting the parents' needs, rather than eating from the shop without prior permission, constitute an act of disbelief (kufr)?

The basic principle is that it is not permissible to consume a Muslim's property without their consent. If you took food items from your father without his knowledge, this constitutes a breach of trust. You must repent and return the value of what you took to its owner (your father or your aunt). It is not a condition to inform him of what happened; rather, it is sufficient to return the right to him by any means. Your dutifulness to your parents and your building of the house do not exempt you from returning financial rights, for filial piety is an obligation in itself, and the salary you agreed upon with your father is only your right.