$6,800 seems steep for just an attic run, I'd get a second bid before doing anything drastic. Knob and tube isn't automatically a death sentence, plenty of old houses in Columbus still have it and people live in them just fine. The real issue is your lender, and a lot of times they just want documentation that it's been dealt with, not necessarily a full rewire of the whole house. An electrician can sometimes just replace the exposed attic section and put it on a junction box, which is way cheaper. Ask the inspector and your realtor about a repair credit first, sellers in this market are often willing to knock a few grand off rather than lose the deal.

Man, my buddy went through the exact same thing last spring with his Revit families. He had everything on one of those little flash drives he kept in his truck, and it snapped in half when he tossed his keys on the seat. He ended up paying some recovery place 400 bucks and they only got back about half of it. Now he runs everything through a cloud folder that syncs on its own and keeps a second copy on a drive that never leaves his desk. The sync part is what saved him, since he never has to remember to plug anything in.