Professor
You sound like a lovely person. Despite your experiences, your wish is to go forward and find ways to value and care for those you meet along the way.
I first visited Mumsnet because my DS had been shunned and sneered at and I was looking for advice. I know how damaging the experience of bullying can be.
The art of cherishing is usually easier if practised reciprocally. Are there people at your work that you could see yourself becoming closer to? And if you do go back home, I wondered whether you had any friendships you could re-establish or if you could think of simple, not-too-overwhelming ways you could make new contacts there? Understandably, you feel wary of people but there will be good, kind people in your old town that would welcome your friendship. If you were to slowly start to form positive bonds with others outside the abusive group, and began to feel valued, you would find yourself automatically getting into the way of cherishing others.
You already have within you an ability to cherish one group of people especially well - those who have also been bullied and abused. I'm not suggesting you go out looking for these people but, when they appear in your life, you will be able to offer them the gift of empathy and understanding. You will be able to cherish them in ways that are not open to those who have not been through what you have been through.
Letting go of the past is desirable. Forgiveness can be helpful in some cases. But don't feel bad if you just can't do either at the moment. Most people would find it difficult without the closure that comes with seeing justice served or at least remorse expressed by the perpetrators. I think you will find in time, as your own life moves forward and you form wholesome, nurturing friendships, that you will be able to let go of the past without consciously willing it to happen. As for forgiveness, I don't personally think it is necessary in every situation. If, however, you want to forgive because you feel it will help you, then it is certainly an avenue you could explore.
So get your cherishing practice in with nice people first. Cherishing those who made your life in your hometown unbearable, if it is ever to be attempted, is a challenge best left until you have achieved your black belt in cherishing and feel secure enough to offer a detached sort of compassion, or even just civility, while protecting yourself from hurt.