Yes, your ISP will know that you run a relay. (If you don't want that, consider running a bridge instead.)  

1) Although the traffic will look the same when you are running a Tor relay as when you are merely using the Tor Browser Bundle, the amount and direction of the traffic will change. When you use TBB, your Tor is only a client. You will have little traffic 'up' (relatively small requests) and more traffic 'down' (the requested content). When you run a relay, the amount of traffic up and down is much closer together. This will indicate that you run a relay.  

2) The list of relays and their IP addresses is public.