Is it permissible and Islamically encouraged for the family of the deceased to prepare food and invite a group to recite the Qur’an and adhkar (remembrances) and dedicate the reward thereof to the deceased, and then for them to eat from it in the house of the deceased, by analogy with the command to prepare food for the family of the deceased, and based on the aforementioned hadith?

It is not prescribed for the deceased's family to prepare food or invite a group to recite the Qur'an and perform dhikr, then dedicate its reward to the deceased, and subsequently eat from this food. All of this is contrary to the Sunnah (definition). The Sunnah is for food to be prepared for the deceased's family, not for them to prepare it themselves. The Companions considered gathering at the deceased's family and preparing food after burial to be a form of lamentation. Furthermore, the belief that the deceased benefits from this action is incorrect, and if the food is from money that falls short (of what is due to heirs), it is an infringement on their rights. Reciting the Qur'an for the deceased in this manner is an innovated act. As for the aforementioned hadith (definition), it does not indicate the permissibility of the deceased's family preparing food and inviting people to it.