Craigslist can be really frustrating sometimes. I've sold on Craigslist several times. From a car to chickens. But... it seems so much work to sell from CL that sometimes, it doesn't seem worth it. And then when trying to place a legitimate item, these goons keep flagging stuff for no good reason. Ack!
If they are having a hard time making the final decision, then at least you know they valued their family pet. Some people change pets like underwear. These people apparently, to your dismay, are giving it a lot of thought and perhaps shouldn't have actually put the ad up until they arrived at their final decision. I hope it works out for you but I'm on the same page with what is meant to be will be.