i've never done that kind of commute, but I have traveled a fair amount between DC and NYC for work. Acela is definitely the way to go if they will pay for it. On average, it's about 2:45 between NY and DC assuming no issues (and there are frequently issues). It's comfortable, fairly clean, and Wi-Fi is passable. There are clubs at both Union and the new Moynihan station in NY that you would probably want to join until you have status. Food options are pretty limited at Moynihan but there is a fantastic pizza place on the street next door. Union is a pretty dingy place with few food options.

I've done a couple of stretches in which i've gone to NYC weekly for a few weeks and it's exhausting. I can't imagine doing it regularly.