First he needs to be evaluated by a GI specialist to rule out medical problems for his feeding difficulties. He also should be evaluated by speech and occupational therapies, as he may have oral motor problems or texture aversions - and these can be treated. Second, he needs a good hearing evaluation - human speech is at a different decibel level than most other sounds and some hearing problems can impact only those decibels.
Finally, I really would recommend that he be evaluated by a child psychologist or developmental pediatrician that specialize in children with Autism. What you describe does not scream Autism to me but not responding to his name, inconsistently tuning into other's language, sometimes repeating exactly what others say, and a fascination with certain logos could be warning signs and it is always better to be safe and to know for sure. If your nephew is not yet 3, your local Early Intervention team will evaluation him of free and after 3, the local school district will. But, private evaluations tend to be more thorough and of higher quality. Good luck.
Could be - these symptoms remind me of our nephew who was diagnosed with PDD-NOS which is a high-functioning form of autism. What does your nephew's pediatrican say?