As Amulek finishes his discussion of the resurrection, Zeezrom began to tremble. This indicated that he was spiritually affected by Amulek’s discourse. It was certainly not simply the words, but the spirit that accompanied those words, that caused Zeezrom’s reaction.
Mormon certainly wrote the very last sentence, and probably the last two, or all, of verse 46. The next chapter begins with Alma speaking after noticing Zeerom’s astonishment. That would appear to be an event in close proximity to the ending of Amulek’s discourse. Thus, when Mormon indicates that he could have written more, we are to understand that Amulek continued to speak, but this was all that Mormon decided to include.
This ends the chapter in the 1830 edition. The difference between copied material from Amulek and the next chapter’s copied material from Alma likely influenced Mormon’s decision to create this chapter division.