Re: Dream as though you'll live forever, live as though
Yes, I meant quasi to modify the future participle directly, since this word can function equally as a conjunction and as an adverb. In the latter use it may modify adjectives, adverbs, and participles in particular (since participles basically function, semantically, as subordinate clauses in themselves). Sometimes it even modifies a single noun, in which case it may be translated variously, e.g."a sort of" or "as it were".
However, I should mention that this particular construction, quasi + future participle, does not occur in either Caesar or Cicero, the oft-cited paragon of classical Latin prose style. In fact neither uses future participles much at all outside of periphrastic constructions and the occasional appearance of futurus or venturus as an adjective meaning "future/soon to come". Cicero does use quasi with the present participle, of course, and quite often at that, but only in the poets and the (slightly) later prose authors does the word appear with the future participle (probably on analogy with Greek, or at least through its influence, considering how fond Greek is of using its future participles).
Yet many of these later authors, Seneca and Livy among them, are reputable and well regarded Latinists in their own right, nor do I think we should necessarily limit ourselves so strictly to a pure Ciceronian prose style when an elegant and pithy construction, albeit slightly unclassical, is available for our purposes of translation.