It's perfectly natural to have those feelings about John's family. When you and a partner split, you not only have to say goodbye to each other, but also the families that have been involved.
In most cases (in my experience) the breakup just doesn't allow you any time to resolve things with them before the breakup is final.
You can either relish or detest these dreams. Sometimes they make me sad.
x
My guess is that the crying is a necessary part of grieving your loss. In my experience, divorce can be a more difficult loss to deal with than the death of a loved one. The latter is a less complicated form of grief, I think.
Love you and send you long-distance hugs
xo
Pat