Hola @Lisa !
I know it’s an old topic but I wonder if you could improve your logic and APP or gave up?
I created my own version for these kind of APPs and I could simplify the logic and amount of columns. Of course, I used JS code through some Experimental Code columns to get it.
Try to do it using the Glide’s conventional tools is a nightmare and a mountain of work. I can understand @ThinhDinh perfectly when he stated “… if someone asks me to build that thing again I would never say yes” 
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I basically worked with arrays, put all dates into arrays, sorted them, filtered and looked for those available days/hours using my arrays via JS code and I can say that my APPs are not monsters difficult to maintain or improve (my big concern when I develop an APP or project).
Here you can test my demo version if you want: https://book-us.glideapp.io
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I included a section where you can set up your attendance parameters and control which days/hours you are available to accept a booking. I know there are more cases or settings to handle the non-workings days but I think I have covered 80-90% of cases.
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I hope it helps you if you are still stuck with it.
Feliz día!