You don't see any errors on sketch052? I see "2 missing coincidences found".

Win7, using 18.160

Every once in a while I post this write-up I did when I started. Maybe it will help you.
https://forum.freecadweb.org/viewtopic.php?f=21&t=29179

I tried to watch but I'm thinking I will need a universal translator for that one.

You have issues with your sketch. Sometimes they can be hard to find. Search up validate sketch. If you can't figure it out then post back. I fixed mine and it works great. Here is a clue( see pic). The cutout at 1:00 and 2:00 position have double lines.

I think this a good example to keep track of, I tried my best fixes and nothing works. I tried using a double sketch and lofting a cube which can be more stable and I tried 0.19( not the latest version), that failed also.

I tried to recreate your model, I can't. I don't how you got a thickness on all faces and got it to work. If I select the box and try to apply a thickness I get a "can't apply thickness" error. Maybe you can describe.

It's in Sketcher. Looks similar to the CreateSketch icon.

There it is! That is perfect. Thanks, great idea. Feature request #3.

You mean sketcher should have something like "center selected element in 3D view"? This could indeed be helpful. There is an icon for "View sketch perpendicular to sketch plane". This could become a toggle between its current function and going back to the previous view. Maybe &...

This time I created a midplane solid. You can see what solid is being added to the cutout. This is additive padding, it is adding material to the bottom in the shape you want. Good luck.

You can add a sketch to another face and pad that thru the solid.

Maybe this will help, I copied your sketches into a new file.