You're right. Trump would have to be Time-Travelling Garrosh levels of stupid to bring this up.
The rest depends a lot on the format. If it is what I think i read, the moderator will be asking some very specific questions on some very specific topics. "Email" might not be one of them, which means Trump will have to do a massive leap of logic to connect that to something else, eating a ton of time -- or just flat-out ignore the moderators, who are likely gunning for him to challenge their authority. Trump won't win if he's surrounded.
Trump should also be careful about "throwing stones" about Clinton's poll numbers, She's still ahead nationally, and leading in a lot of major demographics.