I don't understand why you said 休むそう and 休むよう are interchangeable. I've just revised the grammar and understood that～Plain-form + そうです is used for hearsay. And verb of plain-form + ようです is to convey the speaker's subjective conjecture, which is based on the ...
来れない is a variant form of 来られない. Strictly speaking, this form is incorrect. In conversation, however, many people use it for meaning clarity. For 来られない has two meanings; one: someone can’t come; another: someone doesn’t come (politely). But 来れない has one meaning...