You havent brewed it yet?
I'd add some salt maybe at flameout but go easy on it, you can always add more later to taste in the fermentor
Pretzels I would add into the primary. If they are salted pretzels you may not need too much more salt. For sanitation I would just use a sealed bag of a major brand name since I would think they would be better at cleanliness (note that I have NO reason to believe this, its just what I do for coffee beans). Put them in a muslin bag like a dry hop cause theyll get all gunky when absorbing the wort
Caramel is harder. The fat content would mess with fermentation and head retention. I would try getting a flavor extract and adding it maybe when you take your first gravity reading. I like Lorann Oils and I know they have several caramel flavored extracts
