2. The antecedent of the pronoun (i.e., the word to which the pronouns "it" or "they" refers) is "Things," which is plural, so the pronoun must also be plural.
Upon consideration, I agree. Especially if the sentence is spoken, "Things are convoluted [pause] as it is" or turned around (written or spoken) "As it is, things are convoluted." I'll downgrade my judgment to a preference for the double plural to spare the reader the potential clash of number disagreement.