As for (1), one of my decks has ~10,000 mature cards currently gives me ~3-5 reviews per day.
If you plan on sustaining dozens of new cards per day indefinitely, you’ll bury yourself in reviews, but spaced repetition does ensure that if your recall rate is high, review count degrades over time, and eventually becomes negligible. I go through periods of daily new cards when I’m focused on learning something, and periods of review and consolidation. If my daily reviews get over 200, it’s time to let the new cards rest for a while.
If you plan on sustaining dozens of new cards per day indefinitely, you’ll bury yourself in reviews, but spaced repetition does ensure that if your recall rate is high, review count degrades over time, and eventually becomes negligible. I go through periods of daily new cards when I’m focused on learning something, and periods of review and consolidation. If my daily reviews get over 200, it’s time to let the new cards rest for a while.