Short answers, pulled from the story.
William Shakespeare signed legal documents with variations such as Willm Shakp on a deposition from the 11th of May 1612 and Wm Shakspe on a mortgage deed from the 11th of March 1613. His final will dated the 25th of March 1616 contains three signatures reading William Shakspere followed by another instance of William Shakspere and finally By me William Shakspeare.
Fifty-eight quarto editions of Shakespeare's plays appeared before the First Folio collected in 1623 with twenty-two using the unhyphenated spelling Shakespeare and fifteen title pages hyphenating the name as Shake-speare. Richard II saw this form in its second third fourth and fifth quartos between 1598 and 1615 while King Lear's first quarto from 1608 spells the name Shakspeare.
Between 1863 and 1866 Trinity College at Cambridge University published a nine-volume Works of William Shakespeare edited by William George Clark John Glover and William Aldis Wright which established what became known as The Cambridge Shakespeare. The authority of these editions backed by academic credentials caused Shakespeare to dominate publications from that point forward retaining its position to this day despite occasional fringe theories using variant forms.
Edmond Malone declared a preference for the spelling Shakspere in his major sixteen-volume edition of complete works published in 1790 after examining Shakespeare's will and believing the final signature read Shakspere which matched the inscription on Shakespeare's tomb. Delia Bacon published The Philosophy of the Plays of Shakspere Unfolded in London in 1857 using the archaic form to distinguish between the Stratford man and a supposed hidden author.
These six surviving autographs appear on four distinct legal documents from the last five years of his life with most using abbreviated forms like Willm or Wm which was standard practice for scribes of the Elizabethan era. A possibly genuine mark appears on William Lambarde's Archaionomia published in 1568 though it remains smudged and difficult to decipher as Shakspere.