1) "Voting should not be directed as a form of personal self-expression or moral judgement directed in retaliation towards major party candidates who fail to reflect our values, or of a corrupt system designed to limit choices to those acceptable to corporate elites."
The immediate response to this is to ask: "Is not it a matter for my personal integrity to choose my reason for voting?" Surely my reasons for voting (or not doing so) should be determined by my view of the system, the candidates and other matters and it should not be dictated to me that I must vote, in any circumstances, whosoever the candidates may be?" There may be very good reasons why a voter may wish to vote for a candidate including those of moral, social or personal affinity and such reasons should be respected as legitimate - even though I may have my own personal view of why and how people should vote. It seems perfectly reasonable to vote as a means of self-expression, moral judgement or even of disapprobation towards one or more candidates and certainly as part of the calculation in making a judgement as to who to vote for. Chomsky's personal injunction here is no more than an expression of his personal preference and has no validity beyond that, evinces no proof in support of its validity and is of questionable morality.
2) "The exclusive consequence of the act of voting in 2016 will be to marginally increase or decrease the chance of one of the major party candidates winning."
This is not an exclusive consequence: It will marginally increase or decrease the chance of ANY one of the party candidates winning. The implied assumption is that only Trump or Clinton can win and while that is a likelihood, it is by no means the "exclusive" consequence of a vote. Further, the statement's acceptance requires one to make judgements based upon a number of hypothetical factors such as the events occurring between now and the election's close, the conduct of the candidates, the media, the health of the candidates, world events and the motivations of the electorate to which his argument subscribes. It is no more than a political judgement whose reiteration may actually further the likelihood of its proving true. But on that account it seems morally dubious to suggest such a flawed argument which by the author's own admission in  may assist in perpetuating a wrong?
3) Chomsky argues (from error) that Trump will do x, y z if elected. It seems Trump has made such statements, but Chomsky attacks a single candidate here and provides no counter-narrative of what other candidates - including his chosen candidate - will do by contrast. Thus we have nothing by which to measure Trump's proposed actions in terms of their evil, greater or lesser. He could equally have stated that Clinton has said she will intervene in Syria, Iraq and N Korea; or that she has said she will challenge Russia - but once again this would lead us down a dark cul-de-sac of what he/she would do if elected. This is an appeal to false authority in that we have incomplete evidence: we have little reliable knowledge and are in the realms of pure political prejudice.