Five years after the Dominion War ended would be 2380, which is one year prior to the first season of Lower Decks.Five years after the Dominion War would be roughly around the same time as the Lower Decks episode that visited DS9.
Doubtful, as this novel will be more concerned with being accurate to onscreen canon, which has contradicted those comics, more on that with this next part.I do wonder if this will take the comics featuring both Jake and Captain Sisko into account, given Jake having a serious role there, so contributing to his post-DS9 development. It’s not been tradition for the comics and novels to be that connected, but we have seen more connective tissue between mediums in recent years.
In What You Leave Behind, Sisko suggested he could be back in a year, but for some reason only the Novelverse made it happen. In IDW continuity, he came back after 3 years and in Star Trek Online continuity, it's been 36 years and he still hasn't come back.
And now the blurb of The Peacemakers says it's been 5 years since the end of the Dominion War and refers to Sisko as a "departed Emissary".
If I remember correctly, it was Avery Brooks who suggested the line about Sisko coming back in a year because he didn't want to fulfill the stereotype of a black man abandoning his pregnant girlfriend/wife.
Well, we know from the Starfleet Academy trailer that as of the 32nd century, Sisko never returned.