yes the investigation is over. yes, you could sue your mother but do you really want to drag her allegations thru the court? Does she have a bunch of money that you could win? if not, there really is no point in going forward as collections of judgments is very difficult.
If you want to claim your son, you need to take him back to court and have the court change its order. If you don't follow the court order, you can be found in contempt of court and will make it harder in the future to change anything else if the court doesn't trust you to follow its orders. The court can also put sanctions on you for not following its orders up to six months in jail.
it is not unusual to try to settle at any stage...sometimes you can get a better settlement for a confidentiality agreement which is harder to do after the eeoc has been activated. that being said if you don't have confidence in your attorney, you can talk to other attorney and find someone you feel more confident about.