My problem here being that removing the -EC increases the light needed for the camera to find a solution, and I'm already shooting about as slow as I can. Similarly, I'm already shooting at F/2 -- so I can't really get more light that way. Intentional under-exposure (the -EC) and ISO are the only tools available unless I want to carry a tripod (I don't).I would not reduce the exposure anymore as you are limited by the amount of light and for this type of image you want all the exposure you can get. I would ignore using a EC of -1 and raising the iso as you are now prematurely putting a cap on how much DR you can capture when increasing the iso. For this scene you are at the lower limit as to how much more you can reduce the shutter speed.
If you are going to push the image in post I would be using a much lower iso as to reduce the clipping in the stain glass areas and let the DR that the camera has lift the shadows to your liking.
Just remember it is not the camera that captures DR its the size of the exposure and as you apply a - EC or increase the iso you are placing a cap on that DR
And, personal prejudice, I like a deeper DoF in this type of shot. The subject, in a lot of ways, is the entire space. So the DR loses out.


