Is it obligatory to break off relations with former friends, or to invite them to commitment, and what are the limits of this invitation, and when should it be stopped?

You should thank Allah for steadfastness. And part of showing gratitude for this blessing is striving to guide friends and direct them to good, for "That Allah guides one man through you is better for you than red camels." And you must be careful not to associate with old friends if there is a fear of harm from them or of them reminding you of the past, along with the importance of not letting your preoccupation with inviting people distract you from purifying yourself and seeking beneficial knowledge, and maintaining a balance between the right of yourself and the right of others.