You might want to give this coupler a look. Part of the problem on that car. Is the 3 holes in line on the Kadee box are to close to the cars end. This has the same box with just a longer shank coupler. This would allow you to bring the box further back where there is some meat to tap into. Once you settle on a spot that will work. You just need a shim with a through hole. The only threading will be the car itself. It’s best to use a 2mm threaded screw. Which I think is a #52 bit. Use thread cutting oil if you have some for the tap. Any oil is better than nothing. I know some have just used sheet metal screws. If the body can be removed easy enough. You can always just drill right through and secure with a nut. This is right off of Kadee’s site. They are used more in passenger cars. But it will allow you to mount the box back further. Often times. I only mark and drill one hole. Sock it down with a screw to hold it in alignment. Then drill the second hole with a secured box.
Don’t beat yourself up on this. I often end up making 3 mounts just to have two usable ones. It’s tough to get consistency with basic tools. I’m sure there are some sharp guys on the Forum that could easily 3D print the parts. Unfortunately. I’m not one of them.
