thence, whence: As these words mean "from there," "from where," they should not be preceded by the word from as is often erroneously done.
these is, them are: Ungrammatical phrases used by the illiterate for "this is"; "those are." The pronouns should both agree in number with the verb they govern.
these kind, those sort, etc.: Such expressions, though common, are now usually considered altogether wrong. Nouns in the singular require demonstrative adjectives also in the singular. But this may be used instead of these in collective expressions, such as "this ten years." Yet Shakespeare has many instances of this use. Thus, in " Twelfth Night " (act i, sc. 5) he writes "these kind of fools," and in "King Lear" (act ii, sc. 2) a precisely similar expression, "these kind of knaves." In "Othello" (act iii, sc. 3) he has, "these are a kind of men."
think, don't. See don't believe.this or that much: Not elegant perhaps, but still correct or at least passable. A careful speaker would prefer to say "this much," because much being an adjective of quality requires, for its elucidation, not a pronoun but an adverb. It is true that in the expression "this" or "that much," the word "much" could generally, if not always, be omitted without affecting the correctness of the sentence wherein it is used; still the sense would not be precisely the same.