Let your brother know your ex wants to contact him. Let him decide if thats something he wants. If he does then you give your brother your exes number and you have nothing more to do with it. As for the gift card deal. Who cares? You know youre a good person so what if he didn't get you something. Same with his family and ignoring you. Who cares? You shouldn't let that bother you or define you. You did the right thing for you and you will never change what your ex has made them believe. The harder you try the harder on you.
Let it go for your own mental health.