What is the latest time one can eat before Tallit and Tefillin in the morning?
Answer:
One cannot eat after Alos Ha-Shachar. The reason is the prohibition of "lo tochlu al ha-dam" which relates to the obligation of prayer (Shacharis) that begins from Alos Ha-Shachar.
The specific mitzvot of tallit and tefillin do not relate to a prohibition of eating; it is permitted to eat with one's tallit on, and even with one's tefillin, excepting a bread meal (or mezonos).
Best wishes.