My round trip commute varies seasonally since I often take the train part of the way in during the winter. In the winter, the bike part of my route is typically about 30 miles/day. In Spring-Fall, it's around 43 miles/day. When it's nice, I may take a slightly longer, but more scenic route coming home which makes it around 50 miles for the day. I didn't start out doing this distance, though. Over the years, my commutes have been getting longer due to moving further away from the city.

35 miles/day is certainly doable if you're in good shape, but I'd be more concerned about the two lane highway. Part of what makes commuting so fun is that it's relaxing. I'm not sure I'd find 2+ hours/day on the highway very relaxing, but I know others here ride their bikes on roads like that. As for me, I'd rather have 25 miles of small/scenic roads than 17 of heavy traffic, but maybe there are no viable alternate routes in your case.