But he will be unhappy
Sure. He had to give up college and work to support his gifted brother and ailing mom. He gave up sports...he could've been a pro athlete or coach but he had to give up that dream. He was dying inside. Marrying her out of obligation for her support, having kids for her sake are the things that will finally hammer the nails in his coffin. Buried alive. Both Nami and him deserve better.
Yeah it's easier that way, but it could be bad for the longterm.
Don should just stay with Nami and have normal life.