The final two show the frame side(s), front and back.
I have questions:
1. The little stanchions on the front side probably won't print well in 1:32 scale and I suspect, if I do print them, they should be as separate pieces. Comments please.
Do you mean the little plates inside the coupler/buffer? Which diameter do they have?
2. To ensure the frame goes together correctly I am thinking about creating matching holes on the ends of the frame sides and the rear of the frame ends. A piece of brass rod could fit into the holes to keep the frame square and the sides accurately spaced. Yes? No? Better idea?
I'd suggest to add an extrusion at the buffer block's sides and a corresponding notch at the side frame. Otherwise the edge won't come out crisp.

It is usefull to have all "solid" parts like the buffer hollow/open, which means only with the necessary wall thickness to save material. In 1:32 you even may print the completely assembled frame?
The sides have a lot of detail. Will the nuts and bolts, lettering, and other parts print cleanly in a scale as small as 1:32? I'm open to any and all comments. Thanks!
Russ
This depends much on the chosen material and alignment during the process. And the procedure itself - remember my telephone. For the nuts and bolts: Add a center punch from the backside at the bolts' positions. This allows you to drill them out in case they don't come clear and you need to replace them with screw imitations.
Just my five cents.
Cheers,
Volker
P.S.: Great to see you model something!