Saying things are "dream" (dream job, dream house, dream school, adored community) can make problems in itself. Most things in life are a mixed bag - some good, some bad. All jobs involve donkey work as well as exciting stimulating work. But it sounds as if this job is still more interesting and challenging than your old one? And all changes mean some loss as well as gain. You have made a huge change and it's OK to feel sad about the things you have lost, as well as pleased about the things you have gained. But that doesn't mean you made a mistake, and it doesn't mean you can go back. Sure you could return "home" but it wouldn't be the same home you left. Your DS couldn't go back - he has changed, his old friends will have changed and moved on.
You and your DS need to focus on building up your life from now on - doing things you enjoy, meeting new people. A house is only a shell to live in. Maybe you could adjust your "dream job" so as to have spare energy for building up social contacts and community? Or deliberately put some energy each week over the next few months into social contacts on top of your job. A club, a church, a campaign, a drink with your new colleagues, whatever will help you feel more part of a community.
Be careful of giving up what you have for something new... I think we often forget what we we lose in the transition.
But that doesn't mean it was a mistake to make changes. It would be wrong to stagnate in a rut for fear of giving things up, and it sounds as if moving has done at least some good if it brought you a good job and ended a bad relationship. Feeling sad at times is natural! It doesn't sound at all as if you made a mistake.
I think you'll feel a lot better once you have some positive steps in mind, even if they're only very small steps.