In the West Portland OR is probably the best airport to use. I had never heard of anyone using the Newport News airport, but it does look very convenient to the route. Newport News looks like a pretty small airport so you will probably have to fly in to somewhere else like Reagan or Dulles in Washington DC and then get a flight to Newport News. Alternately folks take a bus, ride their bikes, or rent a car to get to the start from one of the DC airports.
The TA is pretty nice without the need for any diversions. We made a few local diversions but only because of specific to us reasons.
As far as how long it will take... That is pretty dependent on you. We took 73 days, which I think is fairly "normal". Some take substantially more or a bit less. Personally I like to have a very open ended schedule if at all possible because I hate to be a slave to a schedule. That may not be an option for you though, given the demands of international travel.