Simplify templating query with Super Table
Someone else will surely better answer the larger question you're asking, but one small point: as you've written it, you're running the filter currentDay|lower many, many times. 

Since that will be static for the duration of the loop, even if Craft/twig doesn't have more efficient ways to handle your query, you should do something like {% set currentDayLower = currentDay|lower %} once around line 4 and then compare {% if day == currentDayLower %} in order to avoid re-doing a filter in a loop.