You should mirror the router switch port and put Wireshark on it using a laptop, etc. That will tell you exactly what traffic is going in/out and in what quantity.
monitor session 1 int f0/1 (ingress/egress port) both
monitor session 1 destination interface f0/2 - where you can connect the laptop to view what the mirror on f0/1 is doing.
You'll capture all traffic going to your WAN, and on a 1 Mbps link you should see it all with no problem. Not sure what Wireshark has as far as traffic analysis these days, but it's free.
Bolding doesn't seem to be consistent, even with edits, sorry.