What should I do with my little brother, and does my father in his grave feel what happened between us?

The apartment does not become yours merely by your father writing it in your name without your taking possession of it and disposing of it during his lifetime, because a gift (Hiba) is not complete until possession is taken (Qabd). If your father dies before possession is taken, the gift becomes void. If the writing was a recommendation for you after his death, it is a bequest to an heir, which is not valid unless the other heirs consent to it. As for your father's assistance to your brother in buying and furnishing the apartment, that is a gift that becomes effective upon the father's death, even if he did not modify it.