I am deeply sorry to hear about your son's story. There are a number of pediatric neurological conditions that your son's clinical and neuro-imaging findings could possibly fit into, but certainly there is no one cause of his problems. (meaning it could be genetic, related to pregnancy abnormalities, a combination of multiple factors,etc...) I would have to personally examine him and look at his films before making any stab at a more definitive diagnosis to be fair to him and your family.
In my personal and professional opinion, I would not give up on this child either. Of course, he's a special needs child who will need constant care and attention for the rest of his life which may very well be significantly less than a normal life span. But as physicians, we can only give our best guesses as to how long someone has to live based on experience and the medical literature. The meaning of DNR is confusing and different among the various states. In Ohio, there are two kinds. One is "DNR arrest" which means no heroic measures like CPR in the event of a life threatening situation. "DNR comfort care" is usually reserved for patients whose death is imminent, such as an 80 year old man who had a large bleed in his brain with no hope for any meaningful recovery. The family in that case will put him on comfort measures only such as IV morphine, with no treatment of infections or complications. You will have to talk to your docs about the exact meaning of your DNR (which by the way can always be reversible if the patient or their power of attorney/guardian changes their mind).
As far as pain and suffering go, like any child you'll have to look to your son for signs of fussiness and irritability as evidence of that.
The best thing you can do for your child is to find a good pediatrician or pediatric neurologist who will help you care for him. The final decision for treatment (seizure control, airway protection, feeding, immunizations) is ultimately up to you. I have personally seen parents who are completely dedicated to their child, trying to raise them as best as they can regardless of the horrible prognosis, congenital malformations, and numerous hospitalizations and complications they've endured. Talk to you pediatrician about your concerns.
I truly wish you and your family the best of luck.
Thanks Again, Heather