Although ME-9 is the fast route to Eastern New Brunswick, you're in rural Maine there so there isn't much. The vacation-home money's on the coast along US-1.
The Irving you're referring to is presumably the Irving Big Stop in Baileyville, ME at the intersection of ME-9 and US-1. Tesla has a permit to put a Supercharger there, but given their cost-cutting I'm not expecting it to be built this year.
There are also gas stations in Calais, ME itself.
I'm not sure what "decrepit" gas pump you used. There's a place in Cherryfield, ME that has a couple of old pumps, but I wouldn't call it decrepit. I guess you hit a one-old-pump convenience stores along the route.
It's only 77 miles from Eddington, ME to Baileyville, ME and with a small population in the area people along Route 9 are going to be OK stopping at those convenience stores if they're not regularly heading to Bangor/Brewer, Ellsworth or Baileyville/Calais areas anyway.
We did pretty well in our 2013 Volt on a trip to NS and PE last year. I don't remember the road noise being loud. But we were heading straight to Halifax, NS so were on the highways. What are your tire pressures? And what tires do you have?