Paula the kids have learn to be distrustful to you because they have learned it from their father. The father probably humiliated you in front of them, and blamed you for everything. It's a little game some irresponsible men like to play. It will probably take a long time till they grow up to realized what their father has done to them and you, but with God's help all things are possible. Hang in there and I pray that your son's foster mother will pray for you and your children too. Also that she will teach them how to be respectful to you. You have to gain respect from them by becoming a strong woman in the Lord and respecting yourself first before others can respect you, including your family and co-workers Paula. Stop putting yourself down by always saying, I'm sorry, unless you are sure it was your fault.
Lord lift Paula out of her depression and help her to forgive herself in whatever may had been her soft spot in the marriage to allow her X to treat her the way he has in front of the kids. Bring them all healing and reconciliation with forgiveness and understanding toward one another. Help her to become a strong woman that can face whatever comes her way in life. Also help her at her job, I pray in Jesus name, amen.