The GV90+3 is about 2x the boiler you actually need.
IIRC the PVG3 is no longer made replaced by the ESC-3 (power vented sealed combustion, which can be side-vented to save the cost of the chimney liner) and ES2-3 (atmospheric- but can be B-vented) which are also 2x the boiler you really need.
The 99% outside design temp for Roanoake is +17F, and designing for 0F would be silly, and would oversize the system by more than 25%. Even if you designed EXACTLY to the 99% design conditions using a Manual-J methods you'd still no be cold on those rare nights when it hit zero F. But the boilers you're looking at are all 2x oversized for your likely true heat load.
If I were to believe any of the heat load numbers cited it would be the 29,000BTU/hr, but even that's on the high-side for a 1600' four-square that has better windows and at least some insulation. If you had a mid-winter's power bill with the exact meter reading dates we could use that to MEASURE the heat load of the house or at least put a firm upper bound on it by looking up the heating degree-days that occurred between the reading dates on degreedays.net, and converting kwh/HDD to BTU/degree-hr.
If you've played around with heat load calculation tools at all you'll notice that the uninsulated basement is a significant fraction of the total load. Air sealing and insulating the band joist & foundation sill is important, but insulating the walls to at least a couple feet below grade is too. Read up on it before diving in though- there are plenty of ways to screw it up and create a mold-farm. (I've covered that territory often on the remodel forum on this site, if you want to search it out.)
It might make better economic sense to design the heating system around a condensing hot water heater like the Vertex or Polaris, since you probably have sufficient radiation to deliver the heat at 130F or cooler water, once you've finished your air-sealing & insulation upgrades. With those you get the benefit of cheap PVC venting and 95% thermal efficiency, probably at a comparable or lower installed cost to what you're looking at. You'll need to isolate the potable from the heating loop with a plate heat exchanger, and use a bronze pump on the potable side loop, but these water heaters are designed for combi-applications, and come with the plumbing ports for space heating built in.