Sorry to hear about your struggles with your jobs and stuttering. I very briefly tried a DAF device, and it did somewhat alleviate stuttering, but speaking felt so unnatural that I decided I would rather just stutter. This seems to be a problem with many stuttering "cures" - they're so disruptive that they aren't worth the improvement. Though it's great that you found some benefit! I know of a case of a preacher who used DAF to to improve fluency only during his sermons, but didn't use it in everyday conversations.