As it turns out, I got Visual Studio to build the solution perfectly fine. In-game, however, the object layout for Gamma's Emerald Coast is still at default. Whatever the problem is, it has to do with SADXLVL2, StructConverter, or anything else in SA Tools.
So, for the past few hours, I've been following a set of instructions on how to import objects from one stage to another. I'm making a mod that changes the E-Series' textures and puts them into other stages (E-103 in Emerald Coast, E-104 in Lost World, etc.) and managed to use SADXLVL2 and StructConverter from SA Tools perfectly.
The trouble comes with Visual Studio.
So far, I can't build the solution since error messages say that SADXModLoader.h and stdafx.h couldn't be found. I'm using the 2019 version of Visual Studio, so pch.h is used as a precompiled header instead of stdafx.h like in the older versions. I'm told by another error that I have to add pch.h to the solution in some way, but doing that, building the solution and using the .dll in my mod shows no stage layout difference in-game. Not sure if I have to edit the code, follow the steps in a different order, or use an older version of Visual Studio. I'll be open to any advice.