With him being that small at 1.5 years old. I suspect that he was not being fed correctly, or 1 pinky a week. My babies nearly always outgrew pinkies quickly when fed one per week. Then I moved them up the line, peach fuzzies, fuzzies, hoppers, etc. Once on adult mice, they started getting fed once every two weeks. Depending on the individual snake. I will be getting one today that is from a long line of scrawny snakes, and will be continued to be fed once a week, as per a his prior owner who is a good friend's feeding regiment for him.
It is good to hear that the little guy is doing better, but remember that if it falls into power feeding it can cause health issues with the little guy.
And, you are a lot better than I am when it comes to Craigslist posts, because I usually ask them what is going through their minds when they do crazy crap. Like housing a BP and a Corn snake together, and saying that "they love each other," and "they always cuddle".