At the beginning of verse 30 in this passage, the 1920 LDS edition added an and before the now that initiates the sentence, yet it was not marked in the 1920 committee copy (a copy of the 1911 LDS edition used to show the editing changes for the 1920 edition). Nonetheless, the addition of the and seems to have been a conscious change since a comma was also added after the now. There is really no reason to have added the and here. There are hundreds of sentences in the text that begin with and now as well as hundreds that begin with now alone. Moreover, since this sentence in Alma 17:30 refers to what Ammon had been thinking at that moment, the more natural transition is simply now.
Summary: Remove the extra and (as well as the comma after now) that was added in the 1920 LDS edition at the beginning of Alma 17:30.