2. I'm in Davenport and have never carried in Waterloo other than as a passenger in a car driving through so I can't comment on that.
3. Expect the unexpected. People have a wide range of reactions. Some will give you a smile and a thumbs up while others will harass you. Good LE will either not really acknowledge you/watch you from a distance or just ask to see your permit while bad LE will detain/arrest you and take you to court and try to destroy your reputation for perfectly lawful behavior. You can ask Dennis Estell about that. He was dragged through the courts, fined, and still didn't really win.
If these are the questions you're asking, you still have a lot to learn before you start carrying. I'm not saying this to discourage you. Please, CC/OC when you feel comfortable doing so. I wish more people did. Just make sure you know the law well enough that you'd feel comfortable going before a judge or jury and defending yourself against prosecution. The law is still unclear in a few aspects, but clarity comes at the cost of a lot of time, money and(even if only for a short while) liberty. You picked the right place to ask the tough questions. Out of all of the many discussion forums I've seen this place is by far my favorite for getting good information and/or direction on where to look for it.
4. Knives are not covered by preemption, so make sure that you know the law of every jurisdiction you're going to be in(No, I am not kidding, I'm completely serious). Same is true for pepper spray. Tasers/Stun Guns require a PTC just like a handgun. The best thing you can get to defend yourself is knowledge. Take good courses. Find the best information you can. Though a lot of the best knowledge I have I've gotten for free from here on OCDO and YouTube, getting good information for real world application is seldom cheap, but it is a hell of a lot cheaper than bail and a lawyer.
There's a lot of people here who will support you in your decision to OC, but not if you go in without having thought out what consequences come with the decision to do so. There aren't a lot of threads in the Iowa section of this forum. Search for the good ones and read them in your spare time.