Not going to happen. First time forming, second time reporting. There's rules to follow when it comes to Fusion. Most of the time is switching directives and changing the approach. From basic model, to just fast modeling.
I can certainly understand the frustration. You're talking about sometimes waiting for the computation to complete. And, find out it's an error. I get confused too. Sometimes it's a shape of a square. And, the computer takes an hour to produce an error for a chamfer. For example.
But, I can just dive deep why your model will not work here. It's not too complex in the design. I get the history and the highlights of the design.
The design is now, just dirty.
First while cutting corners with the program.
The two rigid lines on the outside are mirrored. And separated. Then they also bow and then bend.
The last thing to worry about. They are lower than the rigid lines on the inside.
This happens to be a problem for that exact tool. Thicken or offset. Because the outside point down, will become an inside large portion corner facing up. And, the exact opposite will happen on the inside. One going down other going up. They collide. You get a hole, instead of thickness. That's what's not happening.

The last part. I found. Is really not going to be fixed. If I split the body in the middle. You got this part in the front that has inverted sides. It's like an S shape. Same, thing happens here. They collide in opposite directions, for a hole.

Going back to your model. I would go back before that Reverse Normal. I have no idea who told you to do that there. But, I actually would fill the back bracket with reverse normal. You're doing the wrong side once again. That's why the entire inline is also like a letter S.

And, After a terrible trial. I have to say. I wouldn't fix this for abduction. Instead just do something else that works. Like this. for example. Because. Let's face it. I don't really see industrial potential design here. And, why not actually add proper and may I add working webbings to the 3D print. You can hollow this as this as 60mm tested.
