>> What are your “hard numbers” on the effectiveness of masks?
Look at Jeremy Howard, et al An evidence review of face masks against COVID-19 published in PNAS Jan 2021. A review of various studies.
The issue includes more than masks – SD, air flow, HVAC. It is clear that all of these significantly reduce risk. My sources include multiple articles on airflow simulation, discussions with a distinguished aerospace engineer, and my own experiments measuring airflows in several rooms, including a shul under controlled conditions (with/without people; with windows/doors opened, far/near vents).