The costs of incorporating are steep (I think the yearly maintenance fee is close to $1k. For a sole proprietor: 0). I'd just start as a sole proprietor for a couple years until you gain a client base and decide it's really what you want to do.
One big thing to consider: you say that you don't want to take other people's orders, but when you're a contractor in a service-based industry, your job is fundamentally to do what everyone else wants you to. Your clients will ask you to do something you find stupid or that you disagree with. If you're unavailable when they need you or you are disagreeable, they'll eventually quit calling. It's not like a job where there's a process or warning before you're fired. Your livelihood will depend on whether your clients are happy with you and your work... and until you have enough clients/work to be sustainable, you may not have a lot of room to turn away work.
I think some people look at freelance as the way to be your own boss, but if anything, it's sort of the opposite. It's more like being an at-home employee except you are also handling sales, accounting, scheduling, etc in addition to your actual job - all while you have multiple bosses who don't know each other or what else you're working on. There's no security - If a client doesn't like you, they'll just move onto the next person. If someone does it cheaper, you could lose a client, too. You may have to work harder to create personal relationships (to retain the work). It's not like being in an office every day where you can just catch up with people periodically. If you're a contractor off-site, you have to be active at maintaining those relationships - in your free time.
If you get fired from a job, there's a level of protection you don't have as a contractor. If you interview for a new job and they call your past employer for info, chances are HR isn't going to mention that you got fired or what happened. They'll verify your dates of employment and likely leave it at that. If you screw up with a client, not only could you be fired, but people talk - especially if it's a small (or local) industry.
What are your options under disability? I'm curious if you could find a job that allowed you to work off-site part of the time. You might be covered from getting fired (and would get time off for disability instead)
(I've had my own service-based company for over 10 years, but go between jobs and being freelance. I love it, but it is a lot more work than it sounds like to be profitable.)