You're doing all of the right things - welcoming your new SIL and making an effort to reconcile with your extended family. The only thing you have control over is your own behaviour - continue to take the high road and treat your extended family with courtesy and respect. If they are petty, vindictive and rude - that's their problem - they should be ashamed at having coerced you into the first marriage when it was against your best interests. At the end of the day they're answerable to God for their actions.
The only thing you should be careful about is ensuring that your husband is forewarned about your family and knows what to expect. You can't make your family be nice to him - but you can make them aware that their rudeness is unacceptable. Your parents should also address any issues with your extended family - they need to show the family that they support your husband.
Good luck!