The meaning of Robinson Crusoe’s “and without with turf”

Solution 1:

Without is an adverb or preposition meaning "outside" as Merriam-Webster shows. It is less common in modern English, but its historical popularity is shown by this dictionary giving this meaning before the modern one, in both the adverb and preposition sections.

It means what you would expect, once you treat it as the opposite of within.

In this context, therefore, it means that there was turf on the outside of the shelter, and the sentence would not have seemed odd at the time.

Solution 2:

This is a parallel construction employing adverbial uses of within and without:

lined within with cables, and [lined] without with turf.

In other words, he had cables running along the inside of the fence and turf running along the outside of it.

You have correctly surmised work as referring to a bulwark or fortification; in the plural, works can refer to any engineered structure.