To what degree can we use Shakespeare's work to assume his personality and life?
It is always dangerous to draw conclusions about an author's personality, or biography, from his fictive characters; by definition they are fictive. Shakespeare is a particularly complex case, because he created so many stage characters, and because we have so few biographical pieces from standard sources. Some scholars see parallels in Prospero (The Tempest); others try to decipher the first-person narrator of the sonnets into some sort of portrait, with limited success. All such connections are "assumptions" with little value. Enjoying Shakespeare's work does not require knowing more about the man (as might be the case with Melville, Conrad, Hawthorne, or Tennessee Williams, etc.).