This is a long story but I need some help Please.?

No you should not give in. It's time to move on, no matter how much you've done, no matter how much you love that boy...he is HER son. You are allowing your sister control because of your feeling for her son. You do not need the drama in your life...it's time to move on...forget about having your nephew as ring bearer because she is not going to allow that to happen....she is going to make you pay for getting custody of her son and making her dance to your rules while you had him. The sooner you accept that, the better it will be for you....Good Luck!