Just make sure you select the option WITH Exchange Security enabled. I'm not sure this is required, but that's what I went with and it works.
Correct. Use Titanium Backup (or something similar) to back up your app data and restore them once you are back up and running on your new ROM. Don't backup or restore System Data, just do the app data for the apps you use (non-google apps, those will be restored automatically). There are links here on Android Central, like this one:
http://forums.androidcentral.com/ve...ting-roms-hacks/192528-how-tibu-easy-way.html
that walk you through using TiBu. There is an app for backing up your text messages as well if you want/need to, I'm not sure what app it is, I never bother saving text messages. Your accounts for Gmail, Play Store, etc (anything Google-related) should be backed up automatically through Google anyway, other than Facebook and Twitter, which you will simply need to add again.
Yes. But check the ROM thread on XDA anyway, the developers always give you instructions on how to correctly flash the ROM.
Good luck, any questions ask away.