The data sheet indicates 580 sessions when using medium complexity codec like G.729 so without knowing anything else about your environment my answer would be yes.
http://www.cisco.com/c/en/us/products/collateral/routers/asr-1000-series-aggregation-...
Seems like the ISP is using a modem/router combo box which is why you're being supplied an internal IP address. You could call your ISP and tell them you want to use your own router and they need to put their modem in bridge mode. As for the router i...
Within the user > change password section you're referencing, click the drop down box towards the top that says PIN and you will see Web Password. The box will change from "Voice Mail Pin" to "Web Applications Password"
