I speak no Sigil. However, from what I've been able to pick up, that sounds like what it can do. (Not sure what you mean by "break up into the separate titles"--make a TOC in the one book, or convert into several ebooks?)

I suspect that Sigil is the best tool for what you want, even if it doesn't do everything. It may involve weird options like copying the original book several times & deleting everything you don't want, instead of "split into several ebooks," but other than that, I believe it'll work; I know it can put in tables of contents & allow you to fix typos.

The Mobileread Sigil forum is probably a good place to check.