Good question. I would lean toward using something like Training Peaks to track your training. They don’t use volume only to track training load, but they have some other metrics that could be helpful, Training Stress Score and Training Stress Balance, which could be helpful.
Note that Training Peaks metrics are not decimal-place accurate or predictive. You still have to apply some judgment as to what those numbers mean for you. But once you get used to them, I think they would work well for your schedule.