I think the first question is why have you narrowed things down to IT and security, when you don't know that much about either field? What part of those careers do you like, and what do you think you'll be doing there? Why do you think those two careers are especially good fits for you?
It's possible you may not really know what the work actually involves, so those options might not be as good a fit for you as you think.
I don't know what IT security is like, but I can tell you what I know about software dev. I'm not a programmer, but I know a lot of programmers.
1. What is the typical work enviornment for either? Which tends to offer more stress, more freedom, etc?
Stress on a developer depends on the size of the company and what you're responsible for. The more senior you are, the more responsibilities you have, and you become the go-to person for more things. That leads to more stress, and more people randomly jumping on you to go "hey, can you handle this thing" while you're trying to work on something else. Very high-level developers eventually spend so much time in meetings that they barely actually touch code anymore.
Freedom also depends on your rank and position. If you're lower ranking, you might just be tasked to implement something that was decided above you, so you don't have much freedom on that end (but not much thought required on your part either, which some people like). If you're higher up, you may be expected to figure out how to solve a particular problem, which means more freedom on your end.
Because programming is such a huge field, the environment is also very different. Generally, the more closely your work affects end-users, the more scrutiny you're under. If you're working on some obscure under-the-hood stuff that is very far removed from the customer, then maybe no one will notice if it ever breaks or slows down, which means you're under less pressure. If you work on stuff that's very visible to users and customers, then people watch your work much more closely, because people will notice if you screw up.
2. Which tends to have more job openings and opportunities?
My guess is that software dev has far more openings. Offices naturally tend to have way more developers than IT security guys.
3. Which offer more flexible/rotating schedules? I'm officially done with the 8-5 schedule, because I hate the early morning and I especially hate being stuck on the ass-end commute for both going to work and leaving work.
Many software places have flexible schedules, especially smaller startups. Having said that, both IT security and software development involve a fair amount of on-call work or off-hours work, especially for smaller places where each employee often does a little bit of everything.
If your company provides a web service that's on all the time (for example, Netflix) that service does not follow a 9-5 schedule. If it goes down for any reason, someone will have to go take a look at it, no matter what time it is. That person might be you.
4. Which is more likely to offer work at home options? Again, see above.
Depends on the place. Both probably allow for *some* work from home options, but you will rarely get a chance to work entirely from home.
5. How much of the required materials can be learned for free online using various tools/guides, and how much requires going back to school?
Programming can be self-taught with plenty of online courses and practice. I don't know about IT.
Having said that, if you teach yourself programming, make sure to get familiar with good programming practices. There are a lot of things you can do in programming that work fine when you're the only guy working on something, but can cause a lot of trouble in a larger work environment where multiple people are working on the same thing. Making sure your code is readable and easy to maintain by other people is a huge deal.
6. What kind of certs/degrees/licenses should I focus on, and how many of those can be used for either field?
Not sure. A college degree in computer science or software engineering is a very standard thing to have in this field, but outside of that I don't know if there are cheaper certs or college courses or anything.
7. Finally, what are some of the most common job titles for either field? Are there job positions that can have you do a little of both? Depending on the responses for #6, should I be focusing on earning knowledge that can have me doing both IT and Programming in one job?
Development jobs usually go something like "______ Developer" or "______ Software Engineer". For example, "Java Developer", or "Ruby Full Stack Developer", or "Senior Software Engineer". Software engineering is subtly different from programming, but the line is often blurred when it comes to job titles.
I'm also not against learning about a third option that I may not have known about.
Have you thought about system administrator jobs? These are people who set up and manage whole networks, along with making sure things are secure and reliable. It's a smaller pool than programming, but every company needs at least one.
