Hi Michelle,
I understand where you are coming from with your overload and stress. I am currently in the same situation with large classes without administrative support. How I customize my courses in this situation is to offer a wide variety of delivery methods throughout the course. These methods target the different learning preferences of the students so they can feel comfortable working in the different areas as we move through the course. If I stick with only one method I will be able to meet the learning needs of only a few students. Thus, I am customizing instruction but on a larger scale rather than individual student by individual student. This is the best many of us can do with the limitations we work within.
Gary