My brother's wife told him she wanted a divorce. He wanted (and still wants to make it work). They went to a marriage counselor and she wouldn't even participate. Now he finds out (only from the phone company) that she's gone and rented a house and is planning on taking their 4 yr old done and move out 2/1. Can this be considered abandonment ?

No, it is considered a break up and the start for either a separation or a divorce.

He needs to file for joint custody of child, ask for correct amount of visits and time with child and file for divorce.

Not even close. She wants a divorce and is entitled to do what she is doing. He needs to adjust to the fact that the marriage is over and move on.