BTW, I saw that the est. ridership in 5 years of 5M trips yearly or about 13,700 daily.

That equates to about 1K per hour. Doable?

Would the cars be very, very full at peak times to reach that level of ridership?

My guess the initial ridership estimates of 1.8M trip per year will be easily met. That's less than 5K / day or 350 per hour if the system is open 14 hours per day.