Good news! I managed to fix the problem. Turns out I made a typo in the sabers.shader and that caused the error with the .jpg files. I somehow managed to type "rbg" instead of "rgb". After I corrected that, everything worked exactly as intended. Regardless, I am very appreciative of the help and solutions presented on this forum post and I firmly believe they will help me in the future as I continue learning to mod JKA.
SorcererofRhand's post in Lightsaber Core Showing as a Series of Grey Squares In Game (Single Player) was marked as the answer