Accessibility is an excellent reason to choose Windows, probably sufficient even on its own, if you need an accessible system. Accessibility is hard, and requires a ton of resources to do well...Microsoft has been willing and able to expend those resources. I do know users who require assistive technologies to work who use Linux, but it's rare and they're extremely technically savvy themselves (usually software developers).
As for finding help, I usually find it's the opposite, or at least the kind of help I find for Windows is often very cargo cultish. e.g. "I did these fifteen mysterious steps, and my problem when away. I think that's what fixed it." I feel much more in command of the system with Linux. This is, admittedly, at least as much my own depth of knowledge. I've been building products for Linux for two decades, including kernel development, patching system libraries and services, etc. I actually understand Linux systems on a pretty deep level; I don't understand Windows systems, beyond the GUI.
Firewall? Meh. The default firewall on a Fedora system is fine. There are tons of free tools for managing the iptables firewall (and firewalld simplifies management at the expense of flexibility). I never use a UI, though, as it's pretty easy to use once you understand the basic concepts. But, a firewall isn't really the most important part of securing a system.
Application replacements could definitely be an issue, with regard to accessibility. I am more comfortable with Linux options because of familiarity. I'm less productive with the "leading" applications than I am with their Open Source competition in almost every instance. Inkscape is easier for me than Illustrator, Gimp easier than Photoshop, but again it is due to extreme familiarity. Over a decade of use vs. occasional forays into the Adobe products because a designer I'd hired wanted to go back and forth on designs and was using Adobe products.
Sometimes ease of use is just another way of saying "What I'm used to". I'm just much more used to Linux. I used Windows full time for a little under a year after switching from Amiga in 1995, then switched to Linux, and have been using Linux almost exclusively ever since...I have a Windows partition for games and audio recording. Of course, I've been using it almost exclusively all that time because I strongly prefer it and always have, even when it was really rough around the edges and patching and compiling kernels was just a normal part of being a Linux user. I don't miss those days, but the strength of UNIX/Linux over Windows (to me) stood out even then and even with all of the warts.