obligation or gratitude? It has been said that Shakespeare made use of the expression no fewer than fifty-five times, and that the Bible four times contains the utterance "thanks be to God," Shakespeare's use of the word with "much" as an adjective is indeed most forcible—"for this relief much thanks."
than me should never be used for than I. Say, "He is taller than I"; not "He is taller than me."
than whom: A phrase objected to by some grammatical critics, in such locutions as "Cromwell, than whom no man was better skilled in artifice"; but shown to be "a quite classic expression." Formerly than was often but not always used as a preposition, and than whom is probably a survival of such usage. "Than whom" is generally accepted as permissible— probably because the sentence where it occurs can not be mended without reconstruction, and it has abundant literary authority.
that: In construing this word, it must be recollected that it is not only a conjunction but also a pronoun, both demonstrative and relative. The peculiarity of the word is such that it can be used more times in succession than any other word in the English language. Exception having been taken to a certain "that" found in a school-boy's exercise, it was shown that that that that that boy used was right. Dean Alford constructed a sentence on these lines which contained no fewer than nine thats in succession.