The lines "And in the light there I can see / A sleepyhead so close to me" could be understood in two different ways. "So close to me" seems to be meant primarily literally (in physical proximity), but it could also be taken more metaphorically (in the sense of a deep emotional attachment).
In the line "And ev'rything I have is nothing if it can't belong to you," there's a copulative clause that can be simplified to "ev'rything is nothing." Because the subject and the predicate nominative have similar forms (both end in "-thing"), there's a sense of balance between the two halves (despite the opposite meanings of "ev'rything" and "nothing"), and consequently, there's a sense of precision in the sentiment.
