The tracks to disappear, I think it's just a problem with the map. It pretty much goes up to VT and I think it joins the Conn River in Brattleboro.
The Vermonter posts 30-55 along the route, top speed on the Conn River Line is 10mph and you have to deal with Deer field yard and the slow trains there. NECR is willing to keep the track in decent condition in exchange for Amtrak's monthly "rent" check. PAR (Guilford Rail) has very little to no interest in restoring the Conn River line and is loosing business to trucking.
Before the Conn River line went to crap the Vermonter did indeed use it, but as it stands now it is faster to go to Palmer than it is to go down the CT River.
Amtrak does have trackage rights over NECR Bellows Falls, they use the track that goes north, Green Mountain RR uses the track that goes west. Your point about Chester is interesting, but the Vermonter is supposed to be transit for Vermont residents. A second train there might be productive, as the Ethan Allen Express sells out, and the trackage is there, but the main issues are:
NECR in MA is train orders, no signals and almost completely single tracked.
CSX has to agree to grant more slots to trains to use the single tracking between Palmer and Springfield.
The reason it goes through fast through CT is that is Amtrak owned and operated and maintained for probably 70-90mph.
That all I said,
I live in Amherst and go to Umass Amherst. I would LOVE to see 2 Vermonters a day, I would LOVE to see service to Northamtpon, but until Mr. Patrick is willing to put big money into it, throw down with Peter Pan Bus Lines and PAR, nothing will be done. Just be thankful Vermont continues to send Amtrak it's monthly check for the Vermonter, because otherwise there would be no Vermonter.
BTW, if there ever is a second train to Amherst or Northamtpon, it should be called the "Captain Hook LTD" since it will be competing with Peter Pan.