In Shakespeare's plays it is common to find contracted words, such as "o'er", "e'en", "sulph'uous", "ta'en". Is it just a literary device or those words were actually pronounced (in day-to-day speech) that way in Early Modern English?
Those are generally known as poetic tropes. When writing in iambic pentameter, it is necessary to alternate stressed and unstressed syllables, and measure feet to each line. Many of the contractions you see used by Shakespeare and other writers of the period are being employed to make the words fit a particular rhyming or verse scheme.
Some examples are given here, including this line by Donne:
You can see how the contraction makes the fourth foot work properly.