this subject the Standard Dictionary says, ''How, as an adverb, may be used as an interrogative or a relative in any of its senses. In old or vulgar usage it is sometimes nearly equivalent to the conjunction that: either (1) alone, as, he told me how he had been left an orphan; or (2) in the phrases had that and as how; as, he told how that he saw it all; he told me as how I angered him."
however: As an adverb however has proper and elegant use as, "However wise one may be, there are limits to one's knowledge." But its use for how and ever as, "However could he do it?" should be avoided as a vulgarism; while its employment in the sense of "at any rate; at all," as in the example, "He tried to keep me, but I'm going, however," is provincial and archaic.
As a conjunction it should not be used indiscriminately, as it often is used, for but or notwithstanding. Not "He was sick; not, however, so seriously as he thought," but "He was sick, but not so seriously," etc.; since the relation is sharply adversitive. "And Moses said. Let no man leave of it till the morning. Notwithstanding (not but) they harkened not unto Moses"; since the preceding thought is represented as no impediment to the succeeding one. "I have not seen her since our quarrel; however (not but, or notwithstanding), I expect to be recalled every hour"; since the relation is one of concession and simple