Sorry you're having difficulty finding the right pair of running shoes!
I find that the Brooks Cascadia is roomy for my wide forefoot, but snug in the midfoot where your arch is flat, so that could be the reason why you feel the fit isn't right.
For road running shoes, we often talk about pronation, and how a shoe can be designed to support the natural gait of a runner who over-pronates. On the trail, the lateral motion you make when stepping over rocks and roots, plus the more frequent changes in stride length don't allow those over-pronation devices to do their job well, so trail running shoes aren't grouped by "neutral" or "support." It's important to think about stability instead, which can come from the level of cushioning, or the rigidity within the shoe itself.
Some trail running shoes come in waterproof versions which can help with wet weather, mud, snow, and warmth. But the waterproofing in these shoes only goes about an inch near the cuff of the shoe, so if it's really wet or muddy or snowy, your feet will get wet. And, just as waterproof shoes keep water out, they also hold onto moisture if it gets into the shoe. Therefore, many runners choose to wear non-waterproof shoes to let water drain. It's also well to note that most waterproof trail running shoes don't come in wide widths.
To that end, here's a couple of suggestions:
Hoka Speedgoat 4: This high-cushion shoe comes in wide widths, features a Vibram Mega-Grip outsole for excellent traction, and provides a stable platform for running. It also comes in a Gore-Tex waterproof version in a normal width.
Salomon XA Pro 3D V8 GTX: These waterproof trail runners have excellent stability and feature Salomon's quick lace system which can help you dial in an accommodating fit without having the feel of loose laces on your shoe. Salomon uses a plastic shank, which they call the "3D Chassis" which helps diffuse the impact of rocks under your shoe, and control your footstep. It's the same stable chassis used in some of their hiking boots.
Altra Lone Peak 4 RSM: Altra is known for its foot-shaped wide toebox, which might be suitable for your wider feet. The RSM in the name stands for Rain, Snow, Mud, indicating the shoe's eVent waterproofing, and has long been a choice for runners looking to run and hike quickly and securely over technical terrain.
I hope these ideas help! If you have more questions, you can let us know here. We also offer a personal virtual outfitting service should you wish to speak one-on-one with a footwear expert.