What can I use in place of "literal"?

I don't feel like you really need to find a synonym for literal when you're using it in the classical sense, but if you really want to, you could substitute "precise", "actual" or "exact". For example:

• "He prefers to make literal translations" becomes "He prefers to make exact translations"
• "She gave a literal account of the event" becomes "She gave a precise account of the event"

Most synonyms have the same problem. I've seen "truly" used to emphasize figurative language - "The book truly brings the war to life" (or something similar).

You can try "without [any] exaggeration [whatsoever]" or interject "and I'm being completely serious":

• John Doe, without any exaggeration, screamed his head off.
• John Done - and I'm being completely serious - screamed his head off.

Or you could explicitly reject the figurative meaning:

• John Doe screamed his head off. I don't mean this figuratively, that he screamed very loud; he screamed to the point that his head was severed from the rest of his body.

Combining some synonyms might help reinforce the literalness:

• John Doe literally, actually, truly screamed his head off.

None of these solutions are very elegant, so you could just use "literally" and hope enough people will understand (and many will).