Man, that price jump is wild, the venting must have been made of solid gold too. Classic move, quote low to get the truck out there then hit you with the "oh by the way" once you're stuck with cold water. Good on you for telling him no thanks and walking, some of these guys count on people panicking and just paying up. $650 with the permit is a solid deal, your neighbor's guy sounds like a keeper. That first plumber getting short with you says everything you need to know about him.

Three days isn't the fluke, cure time is about temp and humidity not just days.

Ha, I once soaked a shower head in vinegar and felt like a genius chemist, so you're not alone in the late-to-the-party club. The chalk line might just need a new reel more than a soak, but try the vinegar on the metal parts first. My own dumb move was waiting years to try it on grout, so at least we're both catching up.