This is my 220th day. As for your other questions... those answers still lie firmly in what we don't know.
The number of people currently in the dome fluctuates. There were more of us when I first arrived, only a handful during the first couple of weeks of the prison... sometimes we get a large influx of newcomers, others hardly any at all.
I have no idea if there's a pattern to this. It's difficult to keep track when people come and go unnoticed.