This sounds really interesting! To answer your questions:
1. I would say ‘features of DVD’.
2. Don’t know about differences of opinion but my understanding is that it should be diagnosed by a specialist speech SLT which I am definitely not! Hence why I always say ‘features of…’ rather than the diagnostic label.
3. If I suspected DVD I would use the DEAP
4. If I had formally assessed using the DEAP then I would feel reasonably confident about differentially diagnosing. If I hadn’t done this then I would not feel as confident.
5. Nuffield and work on phonological awareness at whatever level is appropriate for the child. I find this is effective but availability of someone to do carryover – e.g. at home or school – makes a huge difference to progress.
6. I know that Nuffield is evidence based but I cannot say I have read any of this evidence myself!