Excellent responses!!! The only thing i would add is that the so-called proscibed readings are part of our daily (and Sunday) liturgies, i.e. the Mass. And show him a daily or Sunday missal with ALL the readings and prayers-it’s amazing the number of scriptural readings that are in a single mass-the Psalms, OT, Gospels, etc. Truly the Mass is an act or worship that is replete with SS.
Ask him how much time at his service is spent on SS readings, and then compare that with a complete Mass. As Catholics, we spend most of our worship (Mass) praying the scriptures!!! Also, I read a One-A-Day Catholic Bible and am on my 6th trip through it. It always amazes me that each reading is almost “fresh”-wish I could retain more!!! I use the One-A-Day Sunday Visitor Bible, but as previously said there are many others to choose from. I also attend a SS class/study. He may well be amazed to learn how much of SS is used in our worship services, as well as the multitude of Catholic SS study aids.
God bless and good luck!!!