Cable #1 is part of the LCD, and is not on the new panel assembly until the LCD is attached to it. So don't worry that you got the wrong part because there is only 2 cables on it initially.
Reply about broken tab on cable #3. I would try using a small piece of clear cellophane(scotch) tape. After getting the cable in the connector, use your third and fourth hands to put a small pre-cut piece of tape on the top of the cable and on to the top of the connector. which should hold it in place until you get it the rest of the way together. I read a note that some non-American models do not have a lock on this piece, so hopefully it will stay in place after assembly.